criyle/codenet-compile-errors huggingface dataset:
Language: C++

#include <iostream>
#include <set>

int main(){
  std::string str; cin >> str;
  set<char> se;
  for(char s:str){
    se.insert(s);
  }
  int ascii_a = 'a';
  for(int a = 0;a < 26;a++){
    if(se.find(ascii_a + a) != se.end()){
      char s = ascii_a + a;
      cout<<s<<endl;
      return 0;
    }

  }
  std::cout<<"None"<<std::endl;
  return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:5:20: error: 'cin' was not declared in this scope; did you mean 'std::cin'?
    5 |   std::string str; cin >> str;
      |                    ^~~
      |                    std::cin
In file included from a.cc:1:
/usr/include/c++/14/iostream:62:18: note: 'std::cin' declared here
   62 |   extern istream cin;           ///< Linked to standard input
      |                  ^~~
a.cc:6:3: error: 'set' was not declared in this scope
    6 |   set<char> se;
      |   ^~~
a.cc:6:3: note: suggested alternatives:
In file included from /usr/include/c++/14/set:63,
                 from a.cc:2:
/usr/include/c++/14/bits/stl_set.h:96:11: note:   'std::set'
   96 |     class set
      |           ^~~
/usr/include/c++/14/set:87:13: note:   'std::pmr::set'
   87 |       using set = std::set<_Key, _Cmp, polymorphic_allocator<_Key>>;
      |             ^~~
a.cc:6:7: error: expected primary-expression before 'char'
    6 |   set<char> se;
      |       ^~~~
a.cc:8:5: error: 'se' was not declared in this scope; did you mean 's'?
    8 |     se.insert(s);
      |     ^~
      |     s
a.cc:12:8: error: 'se' was not declared in this scope
   12 |     if(se.find(ascii_a + a) != se.end()){
      |        ^~
a.cc:14:7: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   14 |       cout<<s<<endl;
      |       ^~~~
      |       std::cout
/usr/include/c++/14/iostream:63:18: note: 'std::cout' declared here
   63 |   extern ostream cout;          ///< Linked to standard output
      |                  ^~~~
a.cc:14:16: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   14 |       cout<<s<<endl;
      |                ^~~~
      |                std::endl
In file included from /usr/include/c++/14/iostream:41:
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~
Language: C++

#include <iostream>
#include <set>

int main(){
  std::string str; cin >> str;
  set<char> se;
  for(char s:str){
    se.insert(s);
  }
  int ascii_a = 'a';
  for(int a = 0;a < 26;a++){
    if(se.find(ascii_a + a) != se.end()){
      char s = ascii_a + a;
      cout<<s<<endl;
      return 0;
    }

  }
  cout<<"None"<<endl;
  return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:5:20: error: 'cin' was not declared in this scope; did you mean 'std::cin'?
    5 |   std::string str; cin >> str;
      |                    ^~~
      |                    std::cin
In file included from a.cc:1:
/usr/include/c++/14/iostream:62:18: note: 'std::cin' declared here
   62 |   extern istream cin;           ///< Linked to standard input
      |                  ^~~
a.cc:6:3: error: 'set' was not declared in this scope
    6 |   set<char> se;
      |   ^~~
a.cc:6:3: note: suggested alternatives:
In file included from /usr/include/c++/14/set:63,
                 from a.cc:2:
/usr/include/c++/14/bits/stl_set.h:96:11: note:   'std::set'
   96 |     class set
      |           ^~~
/usr/include/c++/14/set:87:13: note:   'std::pmr::set'
   87 |       using set = std::set<_Key, _Cmp, polymorphic_allocator<_Key>>;
      |             ^~~
a.cc:6:7: error: expected primary-expression before 'char'
    6 |   set<char> se;
      |       ^~~~
a.cc:8:5: error: 'se' was not declared in this scope; did you mean 's'?
    8 |     se.insert(s);
      |     ^~
      |     s
a.cc:12:8: error: 'se' was not declared in this scope
   12 |     if(se.find(ascii_a + a) != se.end()){
      |        ^~
a.cc:14:7: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   14 |       cout<<s<<endl;
      |       ^~~~
      |       std::cout
/usr/include/c++/14/iostream:63:18: note: 'std::cout' declared here
   63 |   extern ostream cout;          ///< Linked to standard output
      |                  ^~~~
a.cc:14:16: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   14 |       cout<<s<<endl;
      |                ^~~~
      |                std::endl
In file included from /usr/include/c++/14/iostream:41:
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~
a.cc:19:3: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   19 |   cout<<"None"<<endl;
      |   ^~~~
      |   std::cout
/usr/include/c++/14/iostream:63:18: note: 'std::cout' declared here
   63 |   extern ostream cout;          ///< Linked to standard output
      |                  ^~~~
a.cc:19:17: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   19 |   cout<<"None"<<endl;
      |                 ^~~~
      |                 std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~
Language: C++

#include <iostream>
using namespace std;

int main(){
  char aph[26]{};
  while(char c, cin >> c)aph[c-'a']++;
  for(int i=0; i<26; i++){
    if(!aph[i]){
      cout << (char)(i+'a');
      return 0;
    }
  }
  cout << "None";
  return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:6:15: error: expected initializer before ',' token
    6 |   while(char c, cin >> c)aph[c-'a']++;
      |               ^
a.cc:6:15: error: expected ')' before ',' token
    6 |   while(char c, cin >> c)aph[c-'a']++;
      |        ~      ^
      |               )
a.cc:6:15: error: expected primary-expression before ',' token
Language: C++

#include <bits/stdc++.h>
using namespace std;
string s;
bool b[30];
int main() {
    cin >> s;
    for (int i = 0; i < s.length(); ++i) {
        b[s[i] - 'a'] = 1;
    }
    for (int i = 0; i < 26; ++i) {
        if (!b[i]) {
            puts((char)('a' + i));
            return 0;
        }
    }
    puts("None");
    return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:12:18: error: invalid conversion from 'char' to 'const char*' [-fpermissive]
   12 |             puts((char)('a' + i));
      |                  ^~~~~~~~~~~~~~~
      |                  |
      |                  char
In file included from /usr/include/c++/14/cstdio:42,
                 from /usr/include/c++/14/ext/string_conversions.h:45,
                 from /usr/include/c++/14/bits/basic_string.h:4154,
                 from /usr/include/c++/14/string:54,
                 from /usr/include/c++/14/bitset:52,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:52,
                 from a.cc:1:
/usr/include/stdio.h:714:30: note:   initializing argument 1 of 'int puts(const char*)'
  714 | extern int puts (const char *__s);
      |                  ~~~~~~~~~~~~^~~
Language: C++

#include <iostream>
#include <cstring>
using namespace std;

int main(){
  char s[1000001];
  cin >> s;
  int b[28];
  for(int i = 0; i < strlen(s); i++){
    if(b[s[i]-'a'+1] == 0){
      b[s[i]-'a'+1] = 1;
    }
  }
  for(int i = 1; i <=s 26; i++){
    if(b[i] == 0){
      printf("%c\n",'a'-1+i);
      return 0;
    }
  }
  printf("None\n");

}

Compiler output:
a.cc: In function 'int main()':
a.cc:14:20: error: ISO C++ forbids comparison between pointer and integer [-fpermissive]
   14 |   for(int i = 1; i <=s 26; i++){
      |                  ~~^~~
a.cc:14:23: error: expected ';' before numeric constant
   14 |   for(int i = 1; i <=s 26; i++){
      |                       ^~~
      |                       ;
a.cc:14:26: error: expected ')' before ';' token
   14 |   for(int i = 1; i <=s 26; i++){
      |      ~                   ^
      |                          )
a.cc:14:28: error: 'i' was not declared in this scope
   14 |   for(int i = 1; i <=s 26; i++){
      |                            ^
Language: C++

#include <iostream>
#include <string>
#include <vector>

using namespace std;

int main()
{
  string s; cin >> s;
  vector<char> cv;
  char ans;

  for (int i = 0; i < s.length(); i++) {
    char x = s[i];
    cv.push_back(x);
  }

  sort(cv.begin(), cv.end());
  cv.erase(unique(cv.begin(), cv.end()), cv.end());

  for (int i = 0; i < 26; i++) {
    int asc = 97 + i;
    if (cv[i] != asc) {
      ans = asc;
      break;
    }
  }

  if (ans == '') cout << "None" << endl;
  else      cout << ans << endl;

  return 0;
}


Compiler output:
a.cc:29:14: error: empty character constant
   29 |   if (ans == '') cout << "None" << endl;
      |              ^~
a.cc: In function 'int main()':
a.cc:18:3: error: 'sort' was not declared in this scope; did you mean 'short'?
   18 |   sort(cv.begin(), cv.end());
      |   ^~~~
      |   short
a.cc:19:12: error: 'unique' was not declared in this scope
   19 |   cv.erase(unique(cv.begin(), cv.end()), cv.end());
      |            ^~~~~~
Language: C++

open System
open System.Collections.Generic
open System.Linq
open System

// Following contents are my library. The Main processes are on the bottom of this code.

let puts = Console.WriteLine : 'a -> unit
let put = Console.Write : 'a -> unit
let Read() = Console.ReadLine()
let Reads () = Console.ReadLine().Split()
let ReadInt () = Read() |> int
let ReadDouble () = Reads() |> (fun x -> x.[0], x.[1])
let ReadTriple () = Reads() |> (fun x -> x.[0], x.[1], x.[2])
let ReadQuadruple () = Reads() |> (fun x -> x.[0], x.[1], x.[2], x.[3])
let FuncDouble f1 f2 (t1, t2) = (f1 t1, f2 t2)
let FuncTriple f1 f2 f3 (t1, t2, t3) = (f1 t1, f2 t2, f3 t3)
let FuncQuadruple f1 f2 f3 f4 (t1, t2, t3, t4) = (f1 t1, f2 t2, f3 t3, f4 t4)

let ReadIntQuadruple () = ReadQuadruple() |> FuncQuadruple int int int int
let ReadIntTriple () = ReadTriple () |> FuncTriple int int int
let ReadIntDouble () = ReadDouble () |> FuncDouble int int
let ensmallen l = l % 1000000007L
let manhattan x y = abs (fst x - fst y) + abs (snd x - snd y)
let sayYESNO b = if b then puts "YES" else puts "NO"


// The main contents of this submission are below this line.

let cs = Read().ToCharArray() |> Seq.distinct
let alphabet = "abcdefghijklmnopqrstuvwxyz".ToCharArray() |> Seq.distinct
let diff = alphabet |> Seq.filter (fun c -> not(Seq.contains c cs)) |> Seq.sort
if Seq.isEmpty diff then puts "None" else Seq.head diff |> puts


Compiler output:
a.cc:8:32: warning: missing terminating ' character
    8 | let puts = Console.WriteLine : 'a -> unit
      |                                ^
a.cc:8:32: error: missing terminating ' character
    8 | let puts = Console.WriteLine : 'a -> unit
      |                                ^~~~~~~~~~
a.cc:9:27: warning: missing terminating ' character
    9 | let put = Console.Write : 'a -> unit
      |                           ^
a.cc:9:27: error: missing terminating ' character
    9 | let put = Console.Write : 'a -> unit
      |                           ^~~~~~~~~~
a.cc:1:1: error: 'open' does not name a type
    1 | open System
      | ^~~~
Language: C++


#include <iostream>
#include <string>
using namespace std;

int main() {
    string S;
    string result = "None";
    cin >> S;

    for (char c='a'; c <= 'z'; ++c){
        if (std::count(S.begin(), S.end(), c) == 0) cout << c << endl;

    }

}

Compiler output:
a.cc: In function 'int main()':
a.cc:12:18: error: 'count' is not a member of 'std'; did you mean 'cout'?
   12 |         if (std::count(S.begin(), S.end(), c) == 0) cout << c << endl;
      |                  ^~~~~
      |                  cout
Language: C++

#define _GLIBCXX_DEBUG
#include <iostream>
#include <cstdio>
#include <cmath>
#include <string>
#include <vector>
#include <utility>
#include <algorithm>
#include <map>
#include <queue>
#include <bitset>

const double EPS = 1e-10;
const double PI  = acos(-1);
const ll     INF = 1 << 30;

int main(int argc, char* argv[])
{
  std::string s;
  std::string::iterator it;
  std::cin >> s;

  char min_char = 'z';
  std::map< char, bool > mc;
  for (char c = 'a'; c <= 'z'; c++) {
    mc[c] = true;
  }

  for (it = s.begin(); it != s.end(); it++) {
    mc[*it] = false;
  }

  std::string ans = "None";
  for (char c = 'a'; c <= 'z'; c++) {
    if (mc[c] == true) {
      ans = c;
      break;
    }
  }

  std::cout << ans << std::endl;

  return 0;
}


Compiler output:
a.cc:15:7: error: 'll' does not name a type
   15 | const ll     INF = 1 << 30;
      |       ^~
Language: C++

#include <bits/stdc++.h>
using namespace std;

bool ch[26];
char str[100001];

int main(){
	scanf("%s",&str);

	for (int i = 0; i < 26; ++i) 	app[i] = false;
	
	for (int i = 0; S[i] != '\0'; ++i) 
		app[S[i] - 'a'] = true;
	
	for (int i = 0; i < 26; ++i) {
		if (!app[i]) {
			printf("%c\n", (char)(i + 'a'));
			return 0;
		}
	}
	cout << "None\n";

	return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:10:41: error: 'app' was not declared in this scope
   10 |         for (int i = 0; i < 26; ++i)    app[i] = false;
      |                                         ^~~
a.cc:12:25: error: 'S' was not declared in this scope
   12 |         for (int i = 0; S[i] != '\0'; ++i)
      |                         ^
a.cc:13:17: error: 'app' was not declared in this scope
   13 |                 app[S[i] - 'a'] = true;
      |                 ^~~
a.cc:16:22: error: 'app' was not declared in this scope
   16 |                 if (!app[i]) {
      |                      ^~~
Language: C++

#include <bits/stdc++.h>
using namespace std;
int main(){
	 string s;
	 cin>>s;
	}
	 vector<bool>a(25);
	 for(int i=0;s.at(i)!='\0';i++){
		a.at( (int)s.at(i)-'a')=1;
	 }
	 for(int i=0;i<27;i++){
		 if(a.at(i)==1){
			 cout<<(char)('a'+i)<<endl;
			 break;
		 }
		 if(i==26){
			 cout<<"None"<<endl;
		 }
	 }
	return 0;
}


Compiler output:
a.cc:8:10: error: expected unqualified-id before 'for'
    8 |          for(int i=0;s.at(i)!='\0';i++){
      |          ^~~
a.cc:8:22: error: 's' does not name a type
    8 |          for(int i=0;s.at(i)!='\0';i++){
      |                      ^
a.cc:8:36: error: 'i' does not name a type
    8 |          for(int i=0;s.at(i)!='\0';i++){
      |                                    ^
a.cc:11:10: error: expected unqualified-id before 'for'
   11 |          for(int i=0;i<27;i++){
      |          ^~~
a.cc:11:22: error: 'i' does not name a type
   11 |          for(int i=0;i<27;i++){
      |                      ^
a.cc:11:27: error: 'i' does not name a type
   11 |          for(int i=0;i<27;i++){
      |                           ^
a.cc:20:9: error: expected unqualified-id before 'return'
   20 |         return 0;
      |         ^~~~~~
a.cc:21:1: error: expected declaration before '}' token
   21 | }
      | ^
Language: C++

#include <bits/stdc++.h>
using namespace std;
int main(){
	 vector<char> s(100000);
	for(int i=0;i<100000;i++){
		cin>>s.at(i);
	}
	 vector<bool>a(25);
	 for(int i=0;s.at(i)!='\0';i++){
		a.at( (int)s.at(i)-'a')=1;
	 }
	 for(int i=0;i<27;i++){
		 if(a.at(i)==1){
			 cout<<(char)('a'+i)<<endl;
			 break;
		 }
			 if(i==26){
				 cout<<"None"<<endl;
			 }
	return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:21:2: error: expected '}' at end of input
   21 | }
      |  ^
a.cc:3:11: note: to match this '{'
    3 | int main(){
      |           ^
Language: C++

#include <bits/stdc++.h>
using namespace std;
int main(){
	 vector<char> s(100000);
	for(int i=0;i<100000;i++){
		cin>>s.at.(i);
	}
	 vector<int>a(25);
	 for(int i=0;s.at(i)!='/0';i++){
		a.at( (int)s.at(i)-'a')=1;
	 }
	 for(int i=0;i<27;i++){
		 if(a.at(i)==1){
			 cout<<(char)'a'+i<<endl;
			 break;
		 }
			 if(i==26){
				 cout<<"None"<<endl;
			 }
	return 0;
}

Compiler output:
a.cc:9:31: warning: multi-character character constant [-Wmultichar]
    9 |          for(int i=0;s.at(i)!='/0';i++){
      |                               ^~~~
a.cc: In function 'int main()':
a.cc:6:24: error: invalid use of member function 'std::vector<char>::at' (did you forget the '()' ?)
    6 |                 cin>>s.at.(i);
      |                      ~~^~
a.cc:21:2: error: expected '}' at end of input
   21 | }
      |  ^
a.cc:3:11: note: to match this '{'
    3 | int main(){
      |           ^
Language: C++

#include <bits/stdc++.h>
using namespace std;
int main(){
	 vector<char> s(100000);
	for(int i=0;i<100000;i++){
		cin>>s.at.(i);
	}
	 vector<int>a(25);
	 for(int i=0;s.at(i)!='/0';i++){
		a.at( s.at(i)-'a')=1;
	 }
	 for(int i=0;i<27;i++){
		 if(a.at(i)==1){
			 cout<<(char)'a'+i<<endl;
			 break;
		 }
			 if(i==26){
				 cout<<"None"<<endl;
			 }
	return 0;
}

Compiler output:
a.cc:9:31: warning: multi-character character constant [-Wmultichar]
    9 |          for(int i=0;s.at(i)!='/0';i++){
      |                               ^~~~
a.cc: In function 'int main()':
a.cc:6:24: error: invalid use of member function 'std::vector<char>::at' (did you forget the '()' ?)
    6 |                 cin>>s.at.(i);
      |                      ~~^~
a.cc:21:2: error: expected '}' at end of input
   21 | }
      |  ^
a.cc:3:11: note: to match this '{'
    3 | int main(){
      |           ^
Language: C++

#include <bits/stdc++.h>
using namespace std;
int main(){
	 vector<char> s(100000);
	for(int i=0;i<100000;i++){
		cin>>s.at.(i);
	}
	 vector<int>a(25);
	 for(int i=0;i!='/0';i++){
		a.at( s.at(i)-'a')=1;
	 }
	 for(int i=0;i<27;i++){
		 if(a.at(i)==1){
			 cout<<'a'+i<<endl;
			 break;
		 }
			 if(i==26){
				 cout<<"None"<<endl;
			 }
	return 0;
}

Compiler output:
a.cc:9:25: warning: multi-character character constant [-Wmultichar]
    9 |          for(int i=0;i!='/0';i++){
      |                         ^~~~
a.cc: In function 'int main()':
a.cc:6:24: error: invalid use of member function 'std::vector<char>::at' (did you forget the '()' ?)
    6 |                 cin>>s.at.(i);
      |                      ~~^~
a.cc:21:2: error: expected '}' at end of input
   21 | }
      |  ^
a.cc:3:11: note: to match this '{'
    3 | int main(){
      |           ^
Language: C++

#include <cstdio>
using namespace std;

int cnt[26];
int main(void){
  int c;
  while (scanf("%c",&c),c>='a'&&c<='z'){
    cnt[c-'a'] |= 1;
  }
  
  for (int i=0; i<26; i++){
    if (c[i]){
      printf("%c\n",c[i]+'a');
      return 0;
    }
  }
  puts("None");
  return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:12:10: error: invalid types 'int[int]' for array subscript
   12 |     if (c[i]){
      |          ^
a.cc:13:22: error: invalid types 'int[int]' for array subscript
   13 |       printf("%c\n",c[i]+'a');
      |                      ^
Language: C++

#include <bits/stdc++.h>

#define o(output) cout << output << endl
#define priolity_queue pq
#define push p
#define top t

using namespace std;

string s;
int a,b,c,d;
char A,B;
map<char,int> mp;

int main(){
  cin>>s;
  for(int i=0;i<s.size();i++)if(mp.count(s[i])==0)mp.insert(make_pair(s[i],0);
  for(char i='a';i<='z';i++)if(mp.count(i)==0){
    o(i);
    return 0;
    }
  o("None"); 
}                                                           


Compiler output:
a.cc: In function 'int main()':
a.cc:17:78: error: expected ')' before ';' token
   17 |   for(int i=0;i<s.size();i++)if(mp.count(s[i])==0)mp.insert(make_pair(s[i],0);
      |                                                            ~                 ^
      |                                                                              )
Language: C++

#include <bits/stdc++.h>

#define o(output) cout << output << endl
#define priolity_queue pq
#define push p
#define top t

using namespace std;

string s;
int a,b,c,d;
char A,B;
map<char,int> mp;

int main(){
  cin>>s;
  for(int i=0;i<s.size();i++)if(mp.count(s[i]==0)mp.insert(make_pair(s[i],0);
  for(char i='a';i<='z';i++)if(mp.count(i)==0)){
    o(i);
    return 0;
    }
  o("None"); 
}                                                           


Compiler output:
a.cc: In function 'int main()':
a.cc:17:50: error: expected ')' before 'mp'
   17 |   for(int i=0;i<s.size();i++)if(mp.count(s[i]==0)mp.insert(make_pair(s[i],0);
      |                                ~                 ^~
      |                                                  )
a.cc:18:47: error: expected primary-expression before ')' token
   18 |   for(char i='a';i<='z';i++)if(mp.count(i)==0)){
      |                                               ^
Language: C++

#include <bits/stdc++.h>

#define o(output) cout << output << endl
#define priolity_queue pq
#define push p
#define top t

using namespace std;

string s;
int a,b,c,d;
char A,B;
map<char,int> mp;

int main(){
  cin>>s;
  for(int i=0;i<s.size();i++){
    if(mp.count(s[i]==0){
      mp.insert(make_pair(s[i],0);
                }
                }
  for(char i='a';i<='z';i++){
    if(mp.count(i)==0)){
    o(i);
    return 0;
    }
                             }
  o("None"); 
}                                                           

Compiler output:
a.cc: In function 'int main()':
a.cc:18:25: error: expected ')' before '{' token
   18 |     if(mp.count(s[i]==0){
      |       ~                 ^
      |                         )
a.cc:21:17: error: expected primary-expression before '}' token
   21 |                 }
      |                 ^
a.cc:23:23: error: expected primary-expression before ')' token
   23 |     if(mp.count(i)==0)){
      |                       ^
Language: C++

#include <bits/stdc++.h>

#define o(output) cout << output << endl
#define priolity_queue pq
#define push p
#define top t

using namespace std;

string s;
int a,b,c,d;
char A,B;
map<char,int> mp;

int main(){
  cin>>s;
  for(int i=0;i<s.size();i++){
    if(mp.count(s[i]==0){
      mp.insert(make_pair(s[i],0);
                }
                }
  for(char i='a';i<='z';i++){
    if(mp.count(i)==0){
    o(i);
    return 0;
    }
                             }
  o("None"); 
}                                                           

Compiler output:
a.cc: In function 'int main()':
a.cc:18:25: error: expected ')' before '{' token
   18 |     if(mp.count(s[i]==0){
      |       ~                 ^
      |                         )
a.cc:21:17: error: expected primary-expression before '}' token
   21 |                 }
      |                 ^
Language: C++

#include <bits/stdc++.h>

#define o(output) cout << output << endl
#define priolity_queue pq
#define push p
#define top t

using namespace std;

string s;
int a,b,c,d;
char A,B;
map<char,int> mp;

int main(){
  cin>>s;
  for(int i=0;i<s.size();i++)if(mp.count(s[i]==0)mp.insert(make_pair(s[i],0);
  for(char i='a';i<='z';i++){
    if(mp.count(i)==0){
    o(i);
    return 0;
    }
                             }
  o("None"); 
}                                                           

Compiler output:
a.cc: In function 'int main()':
a.cc:17:50: error: expected ')' before 'mp'
   17 |   for(int i=0;i<s.size();i++)if(mp.count(s[i]==0)mp.insert(make_pair(s[i],0);
      |                                ~                 ^~
      |                                                  )
Language: C++

#include <bits/stdc++.h>

#define o(output) cout << output << endl
#define priolity_queue pq
#define push p
#define top t

using namespace std;

string s;
int a,b,c,d;
char A,B;
map<char,int> mp;

int main(){
  cin>>s;
  for(int i=0;i<s.size();i++)if(mp.count(s[i]==0)mp.insert(make_pair(s[i],0);
  for(char i='a';i<='z';i++)if(mp.count(i)==0){
    o(i);
    return 0;
    }
  o("None"); 
}                                                           

Compiler output:
a.cc: In function 'int main()':
a.cc:17:50: error: expected ')' before 'mp'
   17 |   for(int i=0;i<s.size();i++)if(mp.count(s[i]==0)mp.insert(make_pair(s[i],0);
      |                                ~                 ^~
      |                                                  )
Language: C++

#include <bits/stdc++.h>

#define o(output) cout << output << endl
#define priolity_queue pq
#define push p
#define top t

using namespace std;

string s;
int a,b,c,d;
char A,B;
map<char,int> mp;

int main(){
  cin>>s;
  for(int i=0;i<s.size();i++)if(mp.count(s[i]==0)mp.insert(make_pair('s[i]',0);
  for(char i='a';i<='z';i++)if(mp.count(i)==0){
    o(i);
    return 0;
    }
  o("None"); 
}                                                           

Compiler output:
a.cc:17:70: warning: multi-character character constant [-Wmultichar]
   17 |   for(int i=0;i<s.size();i++)if(mp.count(s[i]==0)mp.insert(make_pair('s[i]',0);
      |                                                                      ^~~~~~
a.cc: In function 'int main()':
a.cc:17:50: error: expected ')' before 'mp'
   17 |   for(int i=0;i<s.size();i++)if(mp.count(s[i]==0)mp.insert(make_pair('s[i]',0);
      |                                ~                 ^~
      |                                                  )
Language: C++

#include<cstdio>
int main(){
char s[100001]={};
scanf("%s",s);
int a[26]={};
for(int i=0;true;i++){
if(s[i]==0)break;
else a[s[i]-a]++;
}
for(int i=0;i<26;i++){
if(a[i]==0){
printf("%c\n",i+'a');
break;
}
if(i==25)printf("None\n");
}
return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:8:12: error: invalid operands of types 'char' and 'int [26]' to binary 'operator-'
    8 | else a[s[i]-a]++;
      |        ~~~~^~
      |           | |
      |           | int [26]
      |           char
Language: C++

#include <iostream>
#include <algorithm>
#include <string>
#include <set>

using namespace std;
int main() {

    string str;
    int length,i;
    set<char> alphabets[];
    
    cin >> str;

    length = str.length();

    for(i = 0; i<length; i++){
        alphabets.insert(str[i]);
    }
    
    set<char>::iterator it;

     for(i = 'a';i <= 'z'; i++) {
        it = alphabets.find(i);
        if(it == alphabets.end()){
            cout << i << endl;
            return 0;
        }
    }
    cout << "None" << endl;
    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:11:15: error: array size missing in 'alphabets'
   11 |     set<char> alphabets[];
      |               ^~~~~~~~~
a.cc:18:19: error: request for member 'insert' in 'alphabets', which is of non-class type 'std::set<char> [1]'
   18 |         alphabets.insert(str[i]);
      |                   ^~~~~~
a.cc:24:24: error: request for member 'find' in 'alphabets', which is of non-class type 'std::set<char> [1]'
   24 |         it = alphabets.find(i);
      |                        ^~~~
a.cc:25:28: error: request for member 'end' in 'alphabets', which is of non-class type 'std::set<char> [1]'
   25 |         if(it == alphabets.end()){
      |                            ^~~
Language: C++

#include <iostream>
#include <string>

int main(){
  string s;
  cin >> s;
  int num[26] = {};

  for(int i = 0; i < s.size(); i++){
    num[s[i]-'a']++;
  }

  for(int i = 0; i < 26; i++){
    if(num[i] == 0){
      printf("%c\n", 'a'+i);
      return 0;
    }
  }

  cout << "None" << endl;
  return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:5:3: error: 'string' was not declared in this scope
    5 |   string s;
      |   ^~~~~~
a.cc:5:3: note: suggested alternatives:
In file included from /usr/include/c++/14/iosfwd:41,
                 from /usr/include/c++/14/ios:40,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/usr/include/c++/14/bits/stringfwd.h:77:33: note:   'std::string'
   77 |   typedef basic_string<char>    string;
      |                                 ^~~~~~
In file included from /usr/include/c++/14/bits/locale_classes.h:40,
                 from /usr/include/c++/14/bits/ios_base.h:41,
                 from /usr/include/c++/14/ios:44:
/usr/include/c++/14/string:76:11: note:   'std::pmr::string'
   76 |     using string    = basic_string<char>;
      |           ^~~~~~
a.cc:6:3: error: 'cin' was not declared in this scope; did you mean 'std::cin'?
    6 |   cin >> s;
      |   ^~~
      |   std::cin
/usr/include/c++/14/iostream:62:18: note: 'std::cin' declared here
   62 |   extern istream cin;           ///< Linked to standard input
      |                  ^~~
a.cc:6:10: error: 's' was not declared in this scope
    6 |   cin >> s;
      |          ^
a.cc:20:3: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   20 |   cout << "None" << endl;
      |   ^~~~
      |   std::cout
/usr/include/c++/14/iostream:63:18: note: 'std::cout' declared here
   63 |   extern ostream cout;          ///< Linked to standard output
      |                  ^~~~
a.cc:20:21: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   20 |   cout << "None" << endl;
      |                     ^~~~
      |                     std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~
Language: C++

#include <iostream>
#include <algorithm>
#include <cmath>
#include <limits>
#include <vector>
using namespace std;

int main (void) {
  string s;
  cin >> s;
  int box[200];
  for (int i=0; i<=s.size()-1; i++) {
    char c1=s[i];
    int code1= (int)c1;
    box[code1]++;
  }
  for (int i=97; i<=123; i++) {
    if(box[i]==0){
      char ans=(char)i;
      cout << ans;
      break;
    }
    if (i==123) {
      cout << "None";
      break;
    }
}

Compiler output:
a.cc: In function 'int main()':
a.cc:27:2: error: expected '}' at end of input
   27 | }
      |  ^
a.cc:8:17: note: to match this '{'
    8 | int main (void) {
      |                 ^
Language: C++

#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<algorithm>
#include<vector>
#include<functional>
#include<iomanip>
#include<cmath>
#include<queue>
#include<limits>
#include<cassert>
#include<set>
#include<tuple>
#include<map>
#define YES cout<<"YES"<<endl
#define NO cout<<"NO"<<endl
#define Yes cout<<"Yes"<<endl
#define No cout<<"No"<<endl
#define None cout<<"None"<<endl
typedef long long ll;
using namespace std;

int main() {
	string s; cin >> s;
	string t = "abcdefghijklmnopqrstuvwxyz";
	string u = "abcdefghijklmnopqrstuvwxyz";

	for (int i = 0; i < s.size(); ++i) {
		for (int j = 0; j < 26; ++j) {
			if (s[i] == t[j]) u[j] = 'z';
		}
	}
	sort(u.begin(),u.end());
	if (u == zzzzzzzzzzzzzzzzzzzzzzzzzz) None;
	else cout << u[0] << endl;


}


Compiler output:
a.cc: In function 'int main()':
a.cc:35:18: error: 'zzzzzzzzzzzzzzzzzzzzzzzzzz' was not declared in this scope
   35 |         if (u == zzzzzzzzzzzzzzzzzzzzzzzzzz) None;
      |                  ^~~~~~~~~~~~~~~~~~~~~~~~~~
Language: C++

#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<algorithm>
#include<vector>
#include<functional>
#include<iomanip>
#include<cmath>
#include<queue>
#include<limits>
#include<cassert>
#include<set>
#include<tuple>
#include<map>
#define YES cout<<"YES"<<endl
#define NO cout<<"NO"<<endl
#define Yes cout<<"Yes"<<endl
#define No cout<<"No"<<endl
#define None cout<<"None"<<endl
typedef long long ll;
using namespace std;

int main() {
	string s; cin >> s;
	string t = "abcdefghijklmnopqrstuvwxyz";
	string u = "abcdefghijklmnopqrstuvwxyz";

	for (int i = 0; i < s.size(); ++i) {
		for (int j = 0; j < 26; ++j) {
			if (s[i] == t[j]) u[j] = 'z';
		}
	}
	sort(u.begin(),u.end());
	
	if (u = "zzzzzzzzzzzzzzzzzzzzzzzzzz") None;
	else cout << t << endl;


}


Compiler output:
a.cc: In function 'int main()':
a.cc:36:15: error: could not convert 'u.std::__cxx11::basic_string<char>::operator=(((const char*)"zzzzzzzzzzzzzzzzzzzzzzzzzz"))' from 'std::__cxx11::basic_string<char>' to 'bool'
   36 |         if (u = "zzzzzzzzzzzzzzzzzzzzzzzzzz") None;
      |             ~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      |               |
      |               std::__cxx11::basic_string<char>
Language: C++

#include<iostream>
#include<string>
#include<set>
using namespace std;

int main() {
	string s;
	cin >> s;
	string t = "abcdefghijklmnopqrstuvwxyz";
	set<char>scr;
	string ans = "None";
	for (int i = 0;i < s.size();i++) {
		scr.insert(s.at(i));
	}
	for (int i = 0;i < 26;i++) {
		if (scr.find(t.at(i))) {
			ans = t[i];
			break;
		}
	}
	cout << ans << endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:16:29: error: could not convert 'scr.std::set<char>::find((*(const std::set<char>::key_type*)(& t.std::__cxx11::basic_string<char>::at(((std::__cxx11::basic_string<char>::size_type)i)))))' from 'std::set<char>::iterator' {aka 'std::_Rb_tree<char, char, std::_Identity<char>, std::less<char>, std::allocator<char> >::const_iterator'} to 'bool'
   16 |                 if (scr.find(t.at(i))) {
      |                     ~~~~~~~~^~~~~~~~~
      |                             |
      |                             std::set<char>::iterator {aka std::_Rb_tree<char, char, std::_Identity<char>, std::less<char>, std::allocator<char> >::const_iterator}
Language: C++

  #include<iostream>
  #include<iomanip>
  #include<algorithm>

  using namespace std;

>>#define FOR(i,a,b) for (int i=(a);i<(b);++i)
>>#define REP(i,n) FOR(i,0,n)

  int main(){
      string S;
      cin >> S;
      string A = "abcdefghijklmnopqrstuvwxyz"
>>    REP(i,S.length()){
          REP(j,26){
              if(S.empty()){
                  break;
              }else if(S[i]==A[j]){
                  S.erase(S.begin());
              }
          }
      }
      if(S.empty()){
          cout << "None";
      }else{
          cout << S[0];
      }
  }


Compiler output:
a.cc:7:3: error: stray '#' in program
    7 | >>#define FOR(i,a,b) for (int i=(a);i<(b);++i)
      |   ^
a.cc:8:3: error: stray '#' in program
    8 | >>#define REP(i,n) FOR(i,0,n)
      |   ^
a.cc:7:1: error: expected unqualified-id before '>>' token
    7 | >>#define FOR(i,a,b) for (int i=(a);i<(b);++i)
      | ^~
a.cc:7:37: error: 'i' does not name a type
    7 | >>#define FOR(i,a,b) for (int i=(a);i<(b);++i)
      |                                     ^
a.cc:7:43: error: expected unqualified-id before '++' token
    7 | >>#define FOR(i,a,b) for (int i=(a);i<(b);++i)
      |                                           ^~
Language: C++

#include<iostream>
#include<string>
#include<set>
using namespace std;

int main() {
	string s;
	cin >> s;
	string t = "abcdefghijklmnopqrstuvwxyz";
	set<char>scr;
	for (int i = 0;i < s.size();i++) {
		scr.insert(s.at(i));
	}
	for (int i = 0;i < 26;i++) {
		if (t.at(i) != scr[i]) {
			cout << t[i];
			break;
		}else cout << t[i];
	}
	cout << endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:15:35: error: no match for 'operator[]' (operand types are 'std::set<char>' and 'int')
   15 |                 if (t.at(i) != scr[i]) {
      |                                   ^
Language: C++

l = input()

ans = 'None'

for letter in 'abcdefghijklmnopqrstuvwxyz':
    if letter not in l:
        ans = letter
        break

print(ans)

Compiler output:
a.cc:3:7: warning: multi-character character constant [-Wmultichar]
    3 | ans = 'None'
      |       ^~~~~~
a.cc:5:15: warning: multi-character literal with 26 characters exceeds 'int' size of 4 bytes
    5 | for letter in 'abcdefghijklmnopqrstuvwxyz':
      |               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
a.cc:1:1: error: 'l' does not name a type
    1 | l = input()
      | ^
Language: C++

int main() {
    string s;
    cin>>s;
    int num[26]={0};
    int n=s.size();
    for(int i=0;i<n;++i){
        ++num[s[i]-'a'];
    }
    int c=0;
    for(int i=0;num[i]!=0;++i){
        ++c;
    }
    if(c==0) cout<<"None"<<endl;
    else printf("%c",'a'+c);
   
    return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:2:5: error: 'string' was not declared in this scope
    2 |     string s;
      |     ^~~~~~
a.cc:3:5: error: 'cin' was not declared in this scope
    3 |     cin>>s;
      |     ^~~
a.cc:3:10: error: 's' was not declared in this scope
    3 |     cin>>s;
      |          ^
a.cc:13:14: error: 'cout' was not declared in this scope
   13 |     if(c==0) cout<<"None"<<endl;
      |              ^~~~
a.cc:13:28: error: 'endl' was not declared in this scope
   13 |     if(c==0) cout<<"None"<<endl;
      |                            ^~~~
a.cc:14:10: error: 'printf' was not declared in this scope
   14 |     else printf("%c",'a'+c);
      |          ^~~~~~
a.cc:1:1: note: 'printf' is defined in header '<cstdio>'; this is probably fixable by adding '#include <cstdio>'
  +++ |+#include <cstdio>
    1 | int main() {
Language: C++

fajsonlslfepbjtsaayxbymeskptcumtwrmkkinjxnnucagfrg


Compiler output:
a.cc:1:1: error: 'fajsonlslfepbjtsaayxbymeskptcumtwrmkkinjxnnucagfrg' does not name a type
    1 | fajsonlslfepbjtsaayxbymeskptcumtwrmkkinjxnnucagfrg
      | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Language: C++

#include <stdio.h>
#include <string.h>
                                                                                                
  
int main(void){
                                                                                                
   
    int i,j,h,f,g;

    int a[27] = {0};

    char k[27] = "abcdefghijklmnopqrstuvwxyz";
   
    char s[100001] = "";

    char t[2] = "";
   
      
    scanf("%s", s );
   
    
    for( i = 0 ; i < strlen(s) ; i = i + 1 ){

        for( j = i + 1 ; j < strlen(s) ; j = j + 1 ){

            if( s[i] > s[j] ){

                t = s[j];

                s[j] = s[i];

                s[i] = t;

                }

            }

         }
   
    
    for( h = 0 ; h < strlen(s) ; h = h + 1 ){

        for( f = 0 ; f < strlen(k) ; f = f + 1 ){

            if ( strncmp( s + h, k + f, 1 ) == 0 ){

                a[f] += 1;

                }

             }

         }
   

    for( g = 0 ; g < strlen(k) ; g = g + 1 ){

        if( a[g] == 0 ){

            printf("%c\n", k[g] );

            return 0;

            }

        }


    printf("None\n");


    return 0;
                                                          
}

Compiler output:
a.cc: In function 'int main()':
a.cc:28:19: error: incompatible types in assignment of 'char' to 'char [2]'
   28 |                 t = s[j];
      |                 ~~^~~~~~
a.cc:32:24: error: invalid conversion from 'char*' to 'char' [-fpermissive]
   32 |                 s[i] = t;
      |                        ^
      |                        |
      |                        char*
Language: C++

#include <stdio.h>
#include <string.h>
                                                                                                
  
int main(void){
                                                                                                
   
    int i,j,h,f,g;

    int a[27] = {0};

    char k[27] = "abcdefghijklmnopqrstuvwxyz";
   
    char s[100001] = "";

    char t = "";
   
      
    scanf("%s", s );
   
    
    for( i = 0 ; i < strlen(s) ; i = i + 1 ){

        for( j = i + 1 ; j < strlen(s) ; j = j + 1 ){

            if( s[i] > s[j] ){

                t = s[j];

                s[j] = s[i];

                s[i] = t;

                }

            }

         }
   
    
    for( h = 0 ; h < strlen(s) ; h = h + 1 ){

        for( f = 0 ; f < strlen(k) ; f = f + 1 ){

            if ( strncmp( s + h, k + f, 1 ) == 0 ){

                a[f] += 1;

                }

             }

         }
   

    for( g = 0 ; g < strlen(k) ; g = g + 1 ){

        if( a[g] == 0 ){

            printf("%c\n", k[g] );

            return 0;

            }

        }


    printf("None\n");


    return 0;
                                                          
}

Compiler output:
a.cc: In function 'int main()':
a.cc:16:14: error: invalid conversion from 'const char*' to 'char' [-fpermissive]
   16 |     char t = "";
      |              ^~
      |              |
      |              const char*
Language: C

#include<stdio.h>
#include<string.h>
int main()
{
    char N[100];
    char k[27]={'a','b','c','d','e','f','g','h','i','g','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};
    int d,i,j,z=0,x;
    scanf("%s",N);
    x=strlen(N);
    for (j=0;j<x;j++)
    {
        for (i=0;i<26;i++)
        {
           if (k[i]==N[j]) k[i]=0; 
        }
    }
    for (i=0;i<26;i++)
    {
        if (k[i]<='z' && k[i]>='a')
        {
            z=1;
            printf("%c\n",k[i]);
            break;
        }
    if (z==0) printf("None\n");
    return 0;
}

Compiler output:
main.c: In function 'main':
main.c:27:1: error: expected declaration or statement at end of input
   27 | }
      | ^
Language: C++

#include <iostream>
#include <string>

using namespace std;
int main() {
  string s;
  cin >> s;
  
  int cnt[26];
  for(char c : s){
    ++cnt[c - 'a'];
  }
  
  int* it = find(cnt, cnt + 26, 0);
  if(it == cnt + 26){
    cout << "None" << endl;
  }else{
    cout << 'a' + (it - cnt) << endl;
  }
  return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:14:17: error: no matching function for call to 'find(int [26], int*, int)'
   14 |   int* it = find(cnt, cnt + 26, 0);
      |             ~~~~^~~~~~~~~~~~~~~~~~
In file included from /usr/include/c++/14/bits/locale_facets.h:48,
                 from /usr/include/c++/14/bits/basic_ios.h:37,
                 from /usr/include/c++/14/ios:46,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/usr/include/c++/14/bits/streambuf_iterator.h:435:5: note: candidate: 'template<class _CharT2> typename __gnu_cxx::__enable_if<std::__is_char<_CharT2>::__value, std::istreambuf_iterator<_CharT> >::__type std::find(istreambuf_iterator<_CharT>, istreambuf_iterator<_CharT>, const _CharT2&)'
  435 |     find(istreambuf_iterator<_CharT> __first,
      |     ^~~~
/usr/include/c++/14/bits/streambuf_iterator.h:435:5: note:   template argument deduction/substitution failed:
a.cc:14:17: note:   mismatched types 'std::istreambuf_iterator<_CharT>' and 'int*'
   14 |   int* it = find(cnt, cnt + 26, 0);
      |             ~~~~^~~~~~~~~~~~~~~~~~
Language: C++

#define _USE_MATH_DEFINES
#include <math.h>
#include <time.h>
#include <iostream>
#include <string>
#include <vector>
#include <iomanip>
#include <iterator>
#include <algorithm>

using namespace std;

#define repr(i, a, b) for (int i = (int)(a); i < (int)(b); i++)
#define rep(i, n) repr(i, 0, n)
#define reprrev(i, a, b) for (int i = (int)(b) - 1; i >= (int)(a); i++)
#define reprev(i, n) reprrev(i, 0, n)

#define PI M_PI
#define INF 100000000

typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<bool> vb;
typedef vector<string> vs;
typedef vector<vector<int>> vvi;
typedef vector<vector<ll>> vvll;
typedef vector<vector<bool>> vvb;


void main()
{
	string S;
	cin >> S;
	sort(S.begin(), S.end());
	string ans = "None";
	string al = "abcdefghijklmnopqrstuvwxyz";
	int ptr = 0, ptr1 = 0;

	while (ptr < al.length())
	{
		if (al[ptr] != S[ptr1])
		{
			ans = al[ptr];
			break;
		}

		while (al[ptr] == S[ptr1])
		{
			ptr1++;
		}

		ptr++;
	}

	cout << ans << endl;
	
}



Compiler output:
a.cc:31:1: error: '::main' must return 'int'
   31 | void main()
      | ^~~~
Language: C++

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner scanner = new Scanner(System.in);
		char[] lettrs = scanner.nextLine().toCharArray();
		boolean[] exits = new boolean[26];
		
		for (int i = 0; i < exits.length; i++) {
			exits[i] = false;
		}
		for (int i = 0; i< lettrs.length; i++) {
			exits[lettrs[i]-'a'] = true;
		}
		String ans = "None";
		for (int i = 0; i < exits.length; i++) {
			if (!exits[i]) {
				char c = (char)(i+'a');
				ans = String.valueOf(c);
				break;
			}
		}
		
		System.out.println(ans);
		
		
		scanner.close();

	}

}

Compiler output:
a.cc:1:1: error: 'import' does not name a type
    1 | import java.util.Scanner;
      | ^~~~~~
a.cc:1:1: note: C++20 'import' only available with '-fmodules-ts'
a.cc:3:1: error: expected unqualified-id before 'public'
    3 | public class Main {
      | ^~~~~~
Language: C++

#include<stdio.h>
#include<string.h>


int main(){
  char s[100001];
  scanf("%s",s);
  int ans=0;m='a';
  for(int i=0;i<26;i++){
    if(strchr(s,m)==NULL){
      printf("%c\n",m);
      return 0;

  }else{
    m++;
  }
}
printf("None\n");

  return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:8:13: error: 'm' was not declared in this scope
    8 |   int ans=0;m='a';
      |             ^
Language: C++

int main(void) {
  string s;
  cin >> s;
  vector<bool> a(26, false);
  
  for(int i = 0; i < s.length(); ++i) {
    int t = s[i] - 'a';
    a[t] = true;
  }
  
  for(int i = 0; i < 26; ++i) {
    if (!a[i]) {
      cout << (char)('a' + i) << endl;
      return 0;
    }
  }
  cout << "None" << endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:2:3: error: 'string' was not declared in this scope
    2 |   string s;
      |   ^~~~~~
a.cc:3:3: error: 'cin' was not declared in this scope
    3 |   cin >> s;
      |   ^~~
a.cc:3:10: error: 's' was not declared in this scope
    3 |   cin >> s;
      |          ^
a.cc:4:3: error: 'vector' was not declared in this scope
    4 |   vector<bool> a(26, false);
      |   ^~~~~~
a.cc:4:10: error: expected primary-expression before 'bool'
    4 |   vector<bool> a(26, false);
      |          ^~~~
a.cc:8:5: error: 'a' was not declared in this scope
    8 |     a[t] = true;
      |     ^
a.cc:12:10: error: 'a' was not declared in this scope
   12 |     if (!a[i]) {
      |          ^
a.cc:13:7: error: 'cout' was not declared in this scope
   13 |       cout << (char)('a' + i) << endl;
      |       ^~~~
a.cc:13:34: error: 'endl' was not declared in this scope
   13 |       cout << (char)('a' + i) << endl;
      |                                  ^~~~
a.cc:17:3: error: 'cout' was not declared in this scope
   17 |   cout << "None" << endl;
      |   ^~~~
a.cc:17:21: error: 'endl' was not declared in this scope
   17 |   cout << "None" << endl;
      |                     ^~~~
Language: C++

#include <bits/stdc++.h>
using namespace std;

int main(void) {
  string s;
  cin >> s;
  vector<bool> a(26, false);
  
  for(int i = 0; i < s.length(); ++i) {
    int t = s[i] - 'a';
    a[t] = true;
  }
  
  for(int i = 0; i < 26; ++i) {
    if (!a[i]) cout << (char)('a' + i) << endl, return 0;
  }
  cout << "None" << endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:15:49: error: expected primary-expression before 'return'
   15 |     if (!a[i]) cout << (char)('a' + i) << endl, return 0;
      |                                                 ^~~~~~
Language: C++

#include<bits/stdc++.h>
#define r(i,n) for(int i=0;i<n;i++)
using namespace std;
bool used[100001];
int p[1000];
int main(){
	string s;
	cin>>s;
	r(i,s.size())used[s[i]-'a']=1;
	r(i,26){
		if(!used[i]){
			cout<char(i+'a')<<endl;
			return 0;
		}
	}
	cout<<"None"<<endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:12:41: error: invalid operands of types 'char' and '<unresolved overloaded function type>' to binary 'operator<<'
   12 |                         cout<char(i+'a')<<endl;
      |                              ~~~~~~~~~~~^~~~~~
Language: C++

#include <iostream>
#include <algorithm>
using namespace std;
int main(void) {
  string str1, str2 = "abcdefghijklmnopqrstuvwxyz";
  cin >> str1;
  sort(str1.begin(), str1.end());
  for (int i = 0, ptr = 0; i < str1.length(); ptr++) {
    if (str1[i] != str2[ptr]) {
      cout << str2[ptr] << endl;
      return 0;
    }
    while (str1[i] == str2[ptr]) i++;
  }
  if (ptr < str2.length()) {
    cout << str2[ptr] << endl;
  } else {
    cout << "None" << endl;
  }
  return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:15:7: error: 'ptr' was not declared in this scope
   15 |   if (ptr < str2.length()) {
      |       ^~~
Language: C++

#include <iostream>
#include <algorithm>
using namespace std;
int main(void) {
  string str1, str2 = "abcdefghijklmnopqrstuvwxyz";
  cin >> str1;
  sort(str1.begin(), str1.end());
  for (int i = 0, ptr = 0; i < str1.length(); ptr++) {
    if (str1[i] != str2[ptr]) {
      cout << str2[ptr] << endl;
      return 0;
    }
    while (str1[i] == str2[ptr]) i++;
  }
  if (ptr < str.length()) {
    cout << str2[ptr];
  } else {
    cout << "None" << endl;
  }
  return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:15:7: error: 'ptr' was not declared in this scope
   15 |   if (ptr < str.length()) {
      |       ^~~
a.cc:15:13: error: 'str' was not declared in this scope; did you mean 'str2'?
   15 |   if (ptr < str.length()) {
      |             ^~~
      |             str2