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

#include <stdio.h>
int main(void){
char s[100005];
  int count;
  flag[26];
  scanf("%s",s);
  for(count=0;;count++){
  if(s[count]=='a'){flag[0]++;}
    if(s[count]=='b'){flag[1]++;}
    if(s[count]=='c'){flag[2]++;}
    if(s[count]=='d'){flag[3]++;}
    if(s[count]=='e'){flag[4]++;}
    if(s[count]=='f'){flag[5]++;}
    if(s[count]=='g'){flag[6]++;}
    if(s[count]=='h'){flag[7]++;}
    if(s[count]=='i'){flag[8]++;}
    if(s[count]=='j'){flag[9]++;}
    if(s[count]=='k'){flag[10]++;}
    if(s[count]=='l'){flag[11]++;}
    if(s[count]=='m'){flag[12]++;}
    if(s[count]=='n'){flag[13]++;}
    if(s[count]=='o'){flag[14]++;}
    if(s[count]=='p'){flag[15]++;}
    if(s[count]=='q'){flag[16]++;}
    if(s[count]=='r'){flag[17]++;}
    if(s[count]=='s'){flag[18]++;}
    if(s[count]=='t'){flag[19]++;}
    if(s[count]=='u'){flag[20]++;}
    if(s[count]=='v'){flag[21]++;}
    if(s[count]=='w'){flag[22]++;}
    if(s[count]=='x'){flag[23]++;}
    if(s[count]=='y'){flag[24]++;}
    if(s[count]=='z'){flag[25]++;}
  }
  if(flag[0]==0){printf("a");return 0;}
  if(flag[1]==0){printf("b");return 0;}
  if(flag[2]==0){printf("c");return 0;}
  if(flag[3]==0){printf("d");return 0;}
  if(flag[4]==0){printf("e");return 0;}
  if(flag[5]==0){printf("f");return 0;}
  if(flag[6]==0){printf("g");return 0;}
  if(flag[7]==0){printf("h");return 0;}
  if(flag[8]==0){printf("i");return 0;}
  if(flag[9]==0){printf("j");return 0;}
  if(flag[10]==0){printf("k");return 0;}
  if(flag[11]==0){printf("l");return 0;}
  if(flag[12]==0){printf("m");return 0;}
  if(flag[13]==0){printf("n");return 0;}
  if(flag[14]==0){printf("o");return 0;}
  if(flag[15]==0){printf("p");return 0;}
  if(flag[16]==0){printf("q");return 0;}
  if(flag[17]==0){printf("r");return 0;}
  if(flag[18]==0){printf("s");return 0;}
  if(flag[19]==0){printf("t");return 0;}
  if(flag[20]==0){printf("u");return 0;}
  if(flag[21]==0){printf("v");return 0;}
  if(flag[22]==0){printf("w");return 0;}
  if(flag[23]==0){printf("x");return 0;}
  if(flag[24]==0){printf("y");return 0;}
  if(flag[25]==0){printf("z");return 0;}
  printf("None");
  
  
  
  
return 0;
}

Compiler output:
main.c: In function 'main':
main.c:5:3: error: 'flag' undeclared (first use in this function)
    5 |   flag[26];
      |   ^~~~
main.c:5:3: note: each undeclared identifier is reported only once for each function it appears in
Language: C++

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

int main() {
  string s;
  cin >> s;
  for(int c="a"; c<='z'; c++) {
    bool found false;
    for(int i=0; i<s.length(); i++) {
      if(s[i]==c) {
        found=true;
      }
    }
    if(!found) {
      cout << c << endl;
      return 0;
    }
  }
  cout << "None" << endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:7:13: error: invalid conversion from 'const char*' to 'int' [-fpermissive]
    7 |   for(int c="a"; c<='z'; c++) {
      |             ^~~
      |             |
      |             const char*
a.cc:8:16: error: expected initializer before 'false'
    8 |     bool found false;
      |                ^~~~~
a.cc:11:9: error: 'found' was not declared in this scope; did you mean 'round'?
   11 |         found=true;
      |         ^~~~~
      |         round
a.cc:14:9: error: 'found' was not declared in this scope; did you mean 'round'?
   14 |     if(!found) {
      |         ^~~~~
      |         round
Language: C++

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

int main() {
  string s;
  cin >> s;
  for(int c="a"; c<='z'; c++) {
    bool found false;
    for(int i=0; i<s.length(); i++) {
      if(s[i]==c) {
        found=true;
      }
    }
    if(!found) {
      cout << c << endl;
      return 0;
    }
  }
}

Compiler output:
a.cc: In function 'int main()':
a.cc:7:13: error: invalid conversion from 'const char*' to 'int' [-fpermissive]
    7 |   for(int c="a"; c<='z'; c++) {
      |             ^~~
      |             |
      |             const char*
a.cc:8:16: error: expected initializer before 'false'
    8 |     bool found false;
      |                ^~~~~
a.cc:11:9: error: 'found' was not declared in this scope; did you mean 'round'?
   11 |         found=true;
      |         ^~~~~
      |         round
a.cc:14:9: error: 'found' was not declared in this scope; did you mean 'round'?
   14 |     if(!found) {
      |         ^~~~~
      |         round
Language: C++

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

int main(){
  string s,t; cin>>s;
  char a; 
  bool x;
  t='abcdefghijklmnopqrstuvwxyz';
  for(int i=0;i<t.size();i++){
    for(int j=0;j<s.size();j++){
      if(s[j]=t[i])
        t[i]=' ';
    }
  }
  bool ans=false;
  for(int i=0;i<s.size();i++){
    if(s[i]!=' '){
      a=s[i];
      ans=true;
      break;
    }
  }
  if(ans){
    cout<<a<<endl;
  }
  else{
    cout<<"None"<<endl
  }
  return 0;
}

Compiler output:
a.cc:9:5: warning: multi-character literal with 26 characters exceeds 'int' size of 4 bytes
    9 |   t='abcdefghijklmnopqrstuvwxyz';
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
a.cc: In function 'int main()':
a.cc:9:5: warning: overflow in conversion from 'int' to 'char' changes value from '2004384122' to '122' [-Woverflow]
a.cc:28:23: error: expected ';' before '}' token
   28 |     cout<<"None"<<endl
      |                       ^
      |                       ;
   29 |   }
      |   ~
Language: C++

#include<bits/stdc++.h>
#define mins(a,b) a=min(a,b)
#define maxs(a,b) a=max(a,b)
using namespace std;
int main(){
  string s="abcdefghijklmnopqrstuvwxyz";
  string t;
  int s=0;
  char aa;
  cin>>t;
  for(int i=0;i<t.size();i++){
    for(int j=0;j<s.size();j++){
      if(t[i]==s[j])
        s[j]=' ';
    }
  }
  bool ans=false;
  for(int i=0;i<s.size();i++){
    if(s[i]!=' '){
      aa=s[i];
      break;
    }
  }
  if(false)
    cout<<aa<<endl;
  else
    cout<<"None"<<endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:8:7: error: conflicting declaration 'int s'
    8 |   int s=0;
      |       ^
a.cc:6:10: note: previous declaration as 'std::string s'
    6 |   string s="abcdefghijklmnopqrstuvwxyz";
      |          ^
Language: C++

#include <bits/stdc++.h>
using namespace std;
 
/* REPmacro */
#define REP(i,n) for(int i=0,i##_len=(n);i<i##_len;++i)
#define REPR(i,n) for(int i=((int)(n)-1);i>=0;--i)
#define FOR(i,m,n) for(int i=(int)(m);i<(int)(n);++i)
 
/*alias*/
#define ALL(x) (x).begin(),(x).end()
#define SZ(x) ((int)(x).size())
#define F first
#define S second
#define PB push_back
#define MP make_pair 
 
#define y0 y3487465
#define y1 y8687969
#define j0 j1347829
#define j1 j234892
#define next asdnext
#define prev asdprev
 
/*using*/
using ll = long long;
using ull = unsigned long long;
using unsi = unsigned;
using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using pii = pair<int, int>;
using db = double;
using plex = complex<double>;
using vs = vector<string>;
 
/*template*/
template<class T>inline bool amax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>inline bool amin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
 
/* func */
 
/*struct*/
struct aaa{
    aaa(){
        cin.tie(0); ios::sync_with_stdio(0); cout<<fixed<<setprecision(20);
    };
}aaaaaaa;
 
/* const */
const int INF = 1001001001;
const ll LINF = 1001001001001001001ll;
const int MOD = 1e9 + 7; //10^9
const db EPS = 1e-9;
const int dx[] = {0, 1, 0, -1, 1, -1, 1, -1}, dy[] = {1, 0, -1, 0, 1, -1, -1, 1};
 
//#define int ll
//#define int long long
 
signed main()
{
{
  string s; cin >> s;
  string scomp = "abcdefghijklmnopqrstuvwxyz";
  auto ssize = s.size();
  set<char> t;
  REP(i,ssize){
   t.insert(s[i]);
  }
 
  int cnt = 0;
  for(auto itr = t.begin(); itr != t.end(); ++itr){
     if(scomp[cnt] != *itr){
      cout << scomp[cnt];
      return 0;
     }
    
    /*
    ここにzがscompには含まれていて*itrには含まれていない時の条件式を書けばよい
    しかし、普通に解くのと変わらなくなるためsetのありがたみが薄れる。
    何故書く必要があるのかというと、
    *itrはa~yまで含んでいる(つまりzだけ*itrに含まれないとき)、
    このif文だけだとa~yまでしか(つまりzで判定できない)出力できない。
    */
    
   ++cnt;
    //解決。しかし汎用性が無い
    if(cnt == 26 && 'z' != *itr){
      cout << 'z';
      return 0;
    }
  }
  
  
  cout << "None";
  return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:96:2: error: expected '}' at end of input
   96 | }
      |  ^
a.cc:60:1: note: to match this '{'
   60 | {
      | ^
Language: C++

#include <bits/stdc++.h>
using namespace std;
 
/* REPmacro */
#define REP(i,n) for(int i=0,i##_len=(n);i<i##_len;++i)
#define REPR(i,n) for(int i=((int)(n)-1);i>=0;--i)
#define FOR(i,m,n) for(int i=(int)(m);i<(int)(n);++i)
 
/*alias*/
#define ALL(x) (x).begin(),(x).end()
#define SZ(x) ((int)(x).size())
#define F first
#define S second
#define PB push_back
#define MP make_pair 
 
#define y0 y3487465
#define y1 y8687969
#define j0 j1347829
#define j1 j234892
#define next asdnext
#define prev asdprev
 
/*using*/
using ll = long long;
using ull = unsigned long long;
using unsi = unsigned;
using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using pii = pair<int, int>;
using db = double;
using plex = complex<double>;
using vs = vector<string>;
 
/*template*/
template<class T>inline bool amax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>inline bool amin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
 
/* func */
 
/*struct*/
struct aaa{
    aaa(){
        cin.tie(0); ios::sync_with_stdio(0); cout<<fixed<<setprecision(20);
    };
}aaaaaaa;
 
/* const */
const int INF = 1001001001;
const ll LINF = 1001001001001001001ll;
const int MOD = 1e9 + 7; //10^9
const db EPS = 1e-9;
const int dx[] = {0, 1, 0, -1, 1, -1, 1, -1}, dy[] = {1, 0, -1, 0, 1, -1, -1, 1};
 
//#define int ll
//#define int long long
 
signed main()
{
/*  string s; cin >> s;
  string scomp = "abcdefghijklmnopqrstuvwxyz";
  auto ssize = s.size();
  set<char> t;
  REP(i,ssize){
   t.insert(s[i]);
  }*/

/*  for(auto itr = t.begin(); itr != t.end(); ++itr){
   cout << *itr;
  }*/
  /* 同値
     for (auto x : st) {
        cout << x;
    }
  */
/*  int cnt = -1;
  for(auto itr = t.begin(); itr != t.end(); ++itr){
    ++cnt;*/
//    for(int i = cnt; i < scomp.size(); ++i){
//     if(scomp[i] != *itr){
     if(scomp[cnt] != *itr){
      cout << scomp[cnt];
      return 0;
//       break;
//     }
/*    }
  }
  
  
  cout << "None";
  */
    cout << "a";
  return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:82:9: error: 'scomp' was not declared in this scope
   82 |      if(scomp[cnt] != *itr){
      |         ^~~~~
a.cc:82:15: error: 'cnt' was not declared in this scope; did you mean 'int'?
   82 |      if(scomp[cnt] != *itr){
      |               ^~~
      |               int
a.cc:82:24: error: 'itr' was not declared in this scope
   82 |      if(scomp[cnt] != *itr){
      |                        ^~~
a.cc:95:2: error: expected '}' at end of input
   95 | }
      |  ^
a.cc:60:1: note: to match this '{'
   60 | {
      | ^
Language: C++

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

int main(){
  	int i=0,j=0;
	string s;
  	string t="abcdefghijklmnopqrstuvwxyz";
  	cin>>s;
	sort(s.begin(),s.end());
    while(1){
      	i++;
		if(s[i]!=s[j]){
          j++;
          if(s[i]!=s[j]){cout<<s[j]<<endl;return 0;}
          if(j==25){cout<<"None"<<endl;return 0;}
        }
        
}


Compiler output:
a.cc: In function 'int main()':
a.cc:20:2: error: expected '}' at end of input
   20 | }
      |  ^
a.cc:6:11: note: to match this '{'
    6 | int main(){
      |           ^
Language: C++

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

int main(){
  	int i=0,j=0;
	string s;
  	string t="abcdefghijklmnopqrstuvwxyz";
  	cin>>s;
	sort(s.begin(),s.end());
    while(1){
      	i++;
		if(s[i]!=s[j]){
          j++;
          if(s[i]!=s[j]){cout<<s[j]<<endl;return 0;}
        }
        
}

Compiler output:
a.cc: In function 'int main()':
a.cc:10:9: error: 'sort' was not declared in this scope; did you mean 'short'?
   10 |         sort(s.begin(),s.end());
      |         ^~~~
      |         short
a.cc:18:2: error: expected '}' at end of input
   18 | }
      |  ^
a.cc:5:11: note: to match this '{'
    5 | int main(){
      |           ^
Language: Java

public class Main {

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ

		Scanner scanner = new Scanner(System.in);
		String string = scanner.next();

		int num[] = new int[30];
		Arrays.fill(num, 0);
		for(int i = 0; i < string.length(); i++) {
			char c = string.charAt(i);
			num[c - 'a']++;
		}

		String res = "None";
		for(int i = 0; i < 26; i++) {
			if(num[i] == 0) {
				char c = (char)(i + 'a');
				res = String.valueOf(c);
				break;
			}
		}

		System.out.println(res);
	}

}

Compiler output:
Main.java:6: error: cannot find symbol
		Scanner scanner = new Scanner(System.in);
		^
  symbol:   class Scanner
  location: class Main
Main.java:6: error: cannot find symbol
		Scanner scanner = new Scanner(System.in);
		                      ^
  symbol:   class Scanner
  location: class Main
Main.java:10: error: cannot find symbol
		Arrays.fill(num, 0);
		^
  symbol:   variable Arrays
  location: class Main
3 errors
Language: C++

#include<cstdio>

char s[101010];

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

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

Compiler output:
a.cc: In function 'int main()':
a.cc:9:12: error: expected unqualified-id before '=' token
    9 |     for(int=0;i<26;i++){
      |            ^
a.cc:9:12: error: expected ';' before '=' token
    9 |     for(int=0;i<26;i++){
      |            ^
      |            ;
a.cc:9:12: error: expected primary-expression before '=' token
a.cc:9:15: error: 'i' was not declared in this scope
    9 |     for(int=0;i<26;i++){
      |               ^
a.cc:9:19: error: expected ')' before ';' token
    9 |     for(int=0;i<26;i++){
      |        ~          ^
      |                   )
a.cc:9:20: error: 'i' was not declared in this scope
    9 |     for(int=0;i<26;i++){
      |                    ^
a.cc:12:12: error: expected unqualified-id before '=' token
   12 |     for(int=0;s[i]!='\0';i++){
      |            ^
a.cc:12:12: error: expected ';' before '=' token
   12 |     for(int=0;s[i]!='\0';i++){
      |            ^
      |            ;
a.cc:12:12: error: expected primary-expression before '=' token
a.cc:12:25: error: expected ')' before ';' token
   12 |     for(int=0;s[i]!='\0';i++){
      |        ~                ^
      |                         )
Language: C++

#include<cstdio>

char s[101010]

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

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

Compiler output:
a.cc:5:1: error: expected initializer before 'int'
    5 | int main(){
      | ^~~
Language: C++

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

int main() {
  string s;
  cin >> s;
  vector<int> num(26);
  for (int i=0; i<s.size(); i++) {
      int idx;
      idx = ‘s.at(i)’ - 97;
      num.at(idx)++;
  }
  int cnt = 0;
  for (int i=0; i<26; i++) {
  if (num.at(i) == 0) {
char c = i + 97;
cout << c << endl;
break;
}
cout << “None” << endl;
}
}

Compiler output:
a.cc:10:13: error: extended character ‘ is not valid in an identifier
   10 |       idx = ‘s.at(i)’ - 97;
      |             ^
a.cc:10:21: error: extended character ’ is not valid in an identifier
   10 |       idx = ‘s.at(i)’ - 97;
      |                     ^
a.cc:20:9: error: extended character “ is not valid in an identifier
   20 | cout << “None” << endl;
      |         ^
a.cc:20:9: error: extended character ” is not valid in an identifier
a.cc: In function 'int main()':
a.cc:10:13: error: '\U00002018s' was not declared in this scope
   10 |       idx = ‘s.at(i)’ - 97;
      |             ^~
a.cc:20:9: error: '\U0000201cNone\U0000201d' was not declared in this scope
   20 | cout << “None” << endl;
      |         ^~~~~~
Language: C++

#include<iostream>
#include<vector>

using namespace std;

int main(){
    vector<char> str;
        char tmp = "a";
    while(tmp!='\0'){
        cin >> tmp;
        str.push_back(tmp);
    }

    bool check[26];
    for(int i=0;i<26;i++)check[i] = false;
    for(int i=0;i<str.size();i++){
        for(int j=0;j<26;j++){
            if(str[i]==char(int('a')+j))check[j] = true;
        }
    }
    for(int i=0;i<26;i++){
        if(!check[i]){
            cout << char(int('a')+i) << endl;
            return 0;
        }
    }
    cout << "None" << endl;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:8:20: error: invalid conversion from 'const char*' to 'char' [-fpermissive]
    8 |         char tmp = "a";
      |                    ^~~
      |                    |
      |                    const char*
Language: C++

#include<iostream>
#include<algorithm>
#include<cmath>
#include<cstdio>
#include<string>
#include<vector>
#include<list>
#include<set>
#include<cctype>
#define ld long double
#define ll long long int
#define ull unsigned long long int
using namespace std;
template<class T> inline bool chmax(T& a,T b){if(a<b){a=b;return 1;}return 0;}
template<class T> inline bool chmin(T& a,T b){if(a>b){a=b;return 1;}return 0;}
const long long INF=1LL<<60;


int main(void){
	ios::sync_with_stdio(false); cin.tie(0);
	
	string s;
	cin>>s;
	char ch[s.length()];
	int i;
	for(i=0;i<s.length();i++)ch[i]=s[i];
	sort(ch,ch+s.length());
	if(s.length()==1){
		if(ch[0]=='a')cout<<'b'<<endl;
		else cout<<'a'<<endl;
		return 0;
	}
	for(i=1;i<s.length();i++){
		if(ch[i]-ch[i-1]>1){
			if(ch[0]!=a)cout<<'a'<<endl;
			else cout<<char(ch[i-1]+1)<<endl;
			return 0;
		}
	}
	cout<<"None"<<endl;
	
	
	
	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:35:35: error: 'a' was not declared in this scope
   35 |                         if(ch[0]!=a)cout<<'a'<<endl;
      |                                   ^
Language: C++

#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <string>
#include <cstdio>
#include <stack>
#include <functional>
#include <set>
#include <map>

using namespace std;
typedef long long ll;

#define _SI(arr) (sizeof(arr)/sizeof(arr[0])

int main() {
	string s;
	cin >> s;
	int a[26] = { 0 };
	for (ll i = 0; i < s.size(); i++)
	{
		a[s[i] - 'a']++;
	}
	for (const auto&& i : a)
	{
		if (i == 0)
		{
			char p = 'a' + i;
			cout << p << endl;
			exit(0);
		}
	}

	cout << "None" << endl;

}

Compiler output:
a.cc: In function 'int main()':
a.cc:25:31: error: cannot bind rvalue reference of type 'const int&&' to lvalue of type 'int'
   25 |         for (const auto&& i : a)
      |                               ^
Language: C++

#include <bits/stdc++.h>
using namespace std;
#define rep(i,N) for(int i=0;i<int(N);++i)

int main() {
	string S;
	cin>>S;
	string ans = "None";
	rep(i,26){
		char c = 'a'+i;
		if(!(count(all(S),c))){
			ans=c;
			break;
		}
	}
	cout<<ans<<endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:11:28: error: 'all' was not declared in this scope; did you mean 'std::filesystem::perms::all'?
   11 |                 if(!(count(all(S),c))){
      |                            ^~~
      |                            std::filesystem::perms::all
In file included from /usr/include/c++/14/filesystem:51,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:200,
                 from a.cc:1:
/usr/include/c++/14/bits/fs_fwd.h:158:7: note: 'std::filesystem::perms::all' declared here
  158 |       all               =  0777,
      |       ^~~
Language: C++

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

int main() {
  string S;
  cin >> S;
  
  vector<bool> alphabets(26, false);
  
  for (int i = 0; i < S.size(); i++) alphabets.at(S.at(i) - 'a') = true; 
  
  for (int i = 0; i < 26; i++) {
    if (!alphabets.at(i)) {
      cout << char(i + 'a') << endl;
      break;
    } else if (i == 25) {
      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:4:12: note: to match this '{'
    4 | int main() {
      |            ^
Language: C++

#include <iostream>
#include <bits/stdc++.h>
#include <time.h>
#include <sys/timeb.h>
#include <cstdio>
#include <sys/time.h>

using namespace std;
#define ll long long
#define uint unsigned int
#define ulong unsigned long long int

int main(){
	
	stirng s;
	cin >> s;
	int cnt[26];
	for(int i=0;i<26;i++) cnt[i] = 0;
	
	for(auto c : s) cnt[c]++;
	for(int i=0;i<26;i++){
		if(cnt[i] == 0){
			cout << (char)('a' + i) << endl;
			return 0;
		}
	}
	
	cout << "None" << endl;
	
    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:15:9: error: 'stirng' was not declared in this scope
   15 |         stirng s;
      |         ^~~~~~
a.cc:16:16: error: 's' was not declared in this scope
   16 |         cin >> s;
      |                ^
Language: C++

#include <bits/stdc++.h>
using namespace std;
 
 
 
 
int main(){
  char S;
  cin >> S;
  char app = ("abcdefghijklmnopqrstuvwxyz");
  int N = S.length();
  for (int i = 0; i < N; i++){
   S[i] = "ω";
 
  }
  
  for (int i = 0; i < 26; i++){
    if(S[i] != "ω"){
      cout << app[i] << endl;
      return 0;
      
    }
    
  }
  
  cout << "None" << endl;
  return 0;
  
  
 
  }
 



Compiler output:
a.cc: In function 'int main()':
a.cc:10:15: error: invalid conversion from 'const char*' to 'char' [-fpermissive]
   10 |   char app = ("abcdefghijklmnopqrstuvwxyz");
      |              ~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      |               |
      |               const char*
a.cc:11:13: error: request for member 'length' in 'S', which is of non-class type 'char'
   11 |   int N = S.length();
      |             ^~~~~~
a.cc:13:5: error: invalid types 'char[int]' for array subscript
   13 |    S[i] = "ω";
      |     ^
a.cc:18:9: error: invalid types 'char[int]' for array subscript
   18 |     if(S[i] != "ω"){
      |         ^
a.cc:19:18: error: invalid types 'char[int]' for array subscript
   19 |       cout << app[i] << endl;
      |                  ^
Language: C++

#include <bits/stdc++.h>
using namespace std;
 
 
 
 
int main(){
  char S;
  cin >> S;
  char app = ("abcdefghijklmnopqrstuvwxyz");
  int N = S.length();
  for (int i = 0; i < N; i++){
   S[i] = 'ω';
 
  }
  
  for (int i = 0; i < 26; i++){
    if(S[i] != 'ω'){
      cout << app[i] << endl;
      return 0;
      
    }
    
  }
  
  cout << "None" << endl;
  return 0;
  
  
 
  }
 

Compiler output:
a.cc:13:11: warning: multi-character character constant [-Wmultichar]
   13 |    S[i] = 'ω';
      |           ^~~
a.cc:18:16: warning: multi-character character constant [-Wmultichar]
   18 |     if(S[i] != 'ω'){
      |                ^~~
a.cc: In function 'int main()':
a.cc:10:15: error: invalid conversion from 'const char*' to 'char' [-fpermissive]
   10 |   char app = ("abcdefghijklmnopqrstuvwxyz");
      |              ~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      |               |
      |               const char*
a.cc:11:13: error: request for member 'length' in 'S', which is of non-class type 'char'
   11 |   int N = S.length();
      |             ^~~~~~
a.cc:13:5: error: invalid types 'char[int]' for array subscript
   13 |    S[i] = 'ω';
      |     ^
a.cc:18:9: error: invalid types 'char[int]' for array subscript
   18 |     if(S[i] != 'ω'){
      |         ^
a.cc:19:18: error: invalid types 'char[int]' for array subscript
   19 |       cout << app[i] << endl;
      |                  ^
Language: C++

#include <bits/stdc++.h>
using namespace std;
 
 
 
 
int main(){
  string S;
  cin >> S;
  string app = ("abcdefghijklmnopqrstuvwxyz");
  int N = S.length();
  for (int i = 0; i < N; i++){
   S[i] = "ω";
 
  }
  
  for (int i = 0; i < 26; i++){
    if(app[i] != "ω"){
      cout << app[i] << endl;
      return 0;
      
    }
    
  }
  
  cout << "None" << endl;
  return 0;
  
  
 
  }
 

Compiler output:
a.cc: In function 'int main()':
a.cc:13:11: error: invalid conversion from 'const char*' to '__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type' {aka 'char'} [-fpermissive]
   13 |    S[i] = "ω";
      |           ^~~
      |           |
      |           const char*
a.cc:18:15: error: ISO C++ forbids comparison between pointer and integer [-fpermissive]
   18 |     if(app[i] != "ω"){
Language: C++

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




int main(){
  string S;
  string app = abcdefghijklmnopqrstuvwxyz;
  int N = S.length();
  for (int i = 0; i < N; i++){
   S[i] = 0;

  }
  
  for (int i = 0; i < 25; i++){
    if(app[i] != 0){
      cout << app[i] << endl;
      return 0;
      
    }
  }

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

  }

Compiler output:
a.cc: In function 'int main()':
a.cc:9:16: error: 'abcdefghijklmnopqrstuvwxyz' was not declared in this scope
    9 |   string app = abcdefghijklmnopqrstuvwxyz;
      |                ^~~~~~~~~~~~~~~~~~~~~~~~~~
Language: C++

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




int main(){
  string S;
  sting app = abcdefghijklmnopqrstuvwxyz;
  int N = S.length();
  for (int i = 0; i < N; i++){
   S[i] = 0;

  }
  
  for (int i = 0; i < 25; i++){
    if(app[i] != 0){
      cout << app[i] << endl;
      return 0;
      
    }
  }

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

  }

Compiler output:
a.cc: In function 'int main()':
a.cc:9:3: error: 'sting' was not declared in this scope
    9 |   sting app = abcdefghijklmnopqrstuvwxyz;
      |   ^~~~~
a.cc:17:8: error: 'app' was not declared in this scope
   17 |     if(app[i] != 0){
      |        ^~~
Language: C++

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




int main(){
  string S;
  sting app = abcdefghijklmnopqrstuvwxyz;
  int N = S.length();
  for (int i = 0; i < N; i++){
   S[i] = "true";

  }
  
  for (int i = 0; i < 25; i++){
    if(app[i] == "false"){
      cout << app[i] << endl;
      return 0;
      
    }
  }

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

  }

Compiler output:
a.cc: In function 'int main()':
a.cc:9:3: error: 'sting' was not declared in this scope
    9 |   sting app = abcdefghijklmnopqrstuvwxyz;
      |   ^~~~~
a.cc:12:11: error: invalid conversion from 'const char*' to '__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type' {aka 'char'} [-fpermissive]
   12 |    S[i] = "true";
      |           ^~~~~~
      |           |
      |           const char*
a.cc:17:8: error: 'app' was not declared in this scope
   17 |     if(app[i] == "false"){
      |        ^~~
Language: C++

s = gets.chomp.chars.sort
alph = ("a".."z")
ans=""
alph.each do |i|
	if !s.include?(i)
		ans = i
		break
	end
end
puts ans


Compiler output:
a.cc:1:1: error: 's' does not name a type
    1 | s = gets.chomp.chars.sort
      | ^
Language: C++

#include <bits/stdc++.h>
using namespace std;
 
int main() {
  string S;
  cin >> S;
  sort(S.begin(),S.end());
  if(S[0]!='a'){cout << a << endl; return 0;}
  for(int i=0;i<S.size()-1;i++){
    if(S[i+1]-S[i]>=2){
      char ans=S[i]+1;
      cout << ans << endl;
      return 0;
    }
  }
  cout << "None" << endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:8:25: error: 'a' was not declared in this scope
    8 |   if(S[0]!='a'){cout << a << endl; return 0;}
      |                         ^
Language: C

#include<stdio.h>
#include<string.h>
void mozi_sort(char str[], int length) {
	int tmp[10000] = {};
	int memo = 0;
	for (int i = 0; i < length; i++) {
		tmp[(int)str[i]]++;
	}
	for (int i = 0; i < 256; i++) {
		while (tmp[i] > 0) {
			str[memo] = (char)i;
			memo++;
			tmp[i]--;
		}
	}
}
//大小比較(小)
long long int small(long long int a, long long int b) {
	if (a >= b) {
		return b;
	}
	else {
		return a;
	}
}
int main() {
	long long int n, m, num[2000][2] = {}, result=0;
	char str[200005];
	scanf("%s",str);
  	n = strlen(str);
	mozi_sort(str,n);
	for (int i =1; i < n; i++) {
		if (str[i] == str[i - 1] || (int)str[i] == (int)str[i-1] + 1) {
			continue;
		}
		else {
			printf("%c",(str[i-1]+1));
          return 0;
		}
	}
  		if(str[n-1]!='z'){printf("%c",(str[i-1]+1));return 0;}
		printf("None");	
}



Compiler output:
main.c: In function 'main':
main.c:41:52: error: 'i' undeclared (first use in this function)
   41 |                 if(str[n-1]!='z'){printf("%c",(str[i-1]+1));return 0;}
      |                                                    ^
main.c:41:52: note: each undeclared identifier is reported only once for each function it appears in
Language: C

#include<stdio.h>
#include<string.h>
void mozi_sort(char str[], int length) {
	int tmp[10000] = {};
	int memo = 0;
	for (int i = 0; i < length; i++) {
		tmp[(int)str[i]]++;
	}
	for (int i = 0; i < 256; i++) {
		while (tmp[i] > 0) {
			str[memo] = (char)i;
			memo++;
			tmp[i]--;
		}
	}
}
//大小比較(小)
long long int small(long long int a, long long int b) {
	if (a >= b) {
		return b;
	}
	else {
		return a;
	}
}
int main() {
	long long int n, m, num[2000][2] = {}, result=0;
	char str[200005];
	scanf("%s",str);
  	n = strlen(str);
	mozi_sort(str,n);
	for (int i =1; i < n; i++) {
		if (str[i] == str[i - 1] || (int)str[i] == (int)str[i-1] + 1) {
			continue;
		}
		else {
			printf("%c",(str[i-1]+1));
          return 0;
		}
	}
  		if(str[n-1]!=z){printf("%c",(str[i-1]+1));return 0;}
		printf("None");	
}



Compiler output:
main.c: In function 'main':
main.c:41:30: error: 'z' undeclared (first use in this function)
   41 |                 if(str[n-1]!=z){printf("%c",(str[i-1]+1));return 0;}
      |                              ^
main.c:41:30: note: each undeclared identifier is reported only once for each function it appears in
main.c:41:50: error: 'i' undeclared (first use in this function)
   41 |                 if(str[n-1]!=z){printf("%c",(str[i-1]+1));return 0;}
      |                                                  ^
Language: C

#include<stdio.h>
#define NOT_FOUND '8'
int main() {
  char S[10004], ans = NOT_FOUND;
  scanf("%s", &S);
  
  for (char ch = 'a'; ch <= 'z'; ch++) {
    if (ans != NOT_FOUND) break;
    
    int contained = 0;
    for (int i = 0; i < sizeof(S) / sizeof(char); i++) {
      char s = S[i];
      if (s == ch) contained = 1;
    }
    
    if (!contained) ans = ch;
  }
  
  printf("%s\n", ans != NOT_FOUND ? { ans } : "None");
}

Compiler output:
main.c: In function 'main':
main.c:19:37: error: expected expression before '{' token
   19 |   printf("%s\n", ans != NOT_FOUND ? { ans } : "None");
      |                                     ^
Language: C++

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

int main(){
    char s[101000];
    cin >> s;
    bool a[26]={false};
    for(int i=0;s[i]!='\n';i++)a[s[i]-'a']=true;
    for(int i=0;i<26;i++)cout << a[i] << endl;
    for(int i=0;i<26;i++){
        if(!a[i]){
            cout << (char)(i+'a') <<endl;
            return 0;
        }
    }
    cout << "None" << endl;

Compiler output:
a.cc: In function 'int main()':
a.cc:18:28: error: expected '}' at end of input
   18 |     cout << "None" << endl;
      |                            ^
a.cc:6:11: note: to match this '{'
    6 | int main(){
      |           ^
Language: C++

#include<iostream>
#include<algorithm>
#include<string>
#include<math.h>
#include<cmath>
#include<vector>
#include<stack>
#include<queue>
#include<functional>
#include<map>
#include<set>
using namespace std;
#define rep(i,n) for(int i=0;i<(n);i++)

map<string, int> mp;

int main() {
    string s;
    cin >> s;
    bool c[26]=false;
    rep(i, s.size()) {
        c[s[i] - 97] = true;
    }
    int n = 26;
    rep(i, n) {
        if (c[i] == false) {
            char b = i + 'a';
            cout << b << endl;
            return 0;
        }
    }
    cout << "None" << endl;
    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:20:16: error: array must be initialized with a brace-enclosed initializer
   20 |     bool c[26]=false;
      |                ^~~~~
Language: C++

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

using ll = long long;
using ld = long double;
using pii = pair<int, int>;

#define REP(i,n) for(int i=0, i##_len=(n); i<i##_len; ++i)
#define all(x) (x).begin(),(x).end()
#define m0(x) memset(x,0,sizeof(x))

int dx4[4] = {1,0,-1,0}, dy4[4] = {0,1,0,-1};


int main()
{
    string s;
    cin>>s;
    bool ls[26];
    m0(all(ls));

    
    for(int i = 0; i < s.size(); i++)
    {
        ls[s[i]-'a'] =true;
    }
    
    for(int i = 0; i < 26; i++)
    {
        if(s[i]==false)
        {
            cout<<'a'+i<<endl;
            return 0;
        }
    }
    cout<<"None"<<endl;
    

    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:9:20: error: request for member 'begin' in 'ls', which is of non-class type 'bool [26]'
    9 | #define all(x) (x).begin(),(x).end()
      |                    ^~~~~
a.cc:10:22: note: in definition of macro 'm0'
   10 | #define m0(x) memset(x,0,sizeof(x))
      |                      ^
a.cc:20:8: note: in expansion of macro 'all'
   20 |     m0(all(ls));
      |        ^~~
a.cc:9:32: error: request for member 'end' in 'ls', which is of non-class type 'bool [26]'
    9 | #define all(x) (x).begin(),(x).end()
      |                                ^~~
a.cc:10:22: note: in definition of macro 'm0'
   10 | #define m0(x) memset(x,0,sizeof(x))
      |                      ^
a.cc:20:8: note: in expansion of macro 'all'
   20 |     m0(all(ls));
      |        ^~~
a.cc:9:20: error: request for member 'begin' in 'ls', which is of non-class type 'bool [26]'
    9 | #define all(x) (x).begin(),(x).end()
      |                    ^~~~~
a.cc:10:33: note: in definition of macro 'm0'
   10 | #define m0(x) memset(x,0,sizeof(x))
      |                                 ^
a.cc:20:8: note: in expansion of macro 'all'
   20 |     m0(all(ls));
      |        ^~~
a.cc:9:32: error: request for member 'end' in 'ls', which is of non-class type 'bool [26]'
    9 | #define all(x) (x).begin(),(x).end()
      |                                ^~~
a.cc:10:33: note: in definition of macro 'm0'
   10 | #define m0(x) memset(x,0,sizeof(x))
      |                                 ^
a.cc:20:8: note: in expansion of macro 'all'
   20 |     m0(all(ls));
      |        ^~~
Language: C++

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

using namespace std;

int main() {
    string s;
    cin >> s;
    vector<bool> t(26);
    for (int i = 0; i < s.size(); ++i) t.at(s.at(i) - 'a') = 1;
    int pos = find(t.begin(), t.end(), false) - t.begin();
    if (pos == s.size()) cout << "None" << endl;
    else cout << char('a' + pos) << endl;
    return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:12:19: error: no matching function for call to 'find(std::vector<bool>::iterator, std::vector<bool>::iterator, bool)'
   12 |     int pos = find(t.begin(), t.end(), false) - t.begin();
      |               ~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
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:12:19: note:   'std::_Bit_iterator' is not derived from 'std::istreambuf_iterator<_CharT>'
   12 |     int pos = find(t.begin(), t.end(), false) - t.begin();
      |               ~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
Language: C++

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

int main() {

    string s;
    cin >> s;

    set<char> charset;

    for(int i = 0; i < s.size(); i++){
          charset.insert(s.at(i));
    }

   int count = 0;
   for(auto itr = charset.begin(); itr != charset.end(); itr++){
      
      if( *itr != 97+count ){
            char c = 97+count;
            cout << c << endl;
            return 0;
      }

      count++;
   }

   cout << "None" << endl;
   
}



Compiler output:
a.cc:1:27: error: stray '#' in program
    1 | abcdefghijklmnopqrstuvwxyz#include <bits/stdc++.h>
      |                           ^
a.cc:1:1: error: 'abcdefghijklmnopqrstuvwxyz' does not name a type
    1 | abcdefghijklmnopqrstuvwxyz#include <bits/stdc++.h>
      | ^~~~~~~~~~~~~~~~~~~~~~~~~~
a.cc: In function 'int main()':
a.cc:6:5: error: 'string' was not declared in this scope
    6 |     string s;
      |     ^~~~~~
a.cc:7:5: error: 'cin' was not declared in this scope
    7 |     cin >> s;
      |     ^~~
a.cc:7:12: error: 's' was not declared in this scope
    7 |     cin >> s;
      |            ^
a.cc:9:5: error: 'set' was not declared in this scope
    9 |     set<char> charset;
      |     ^~~
a.cc:9:9: error: expected primary-expression before 'char'
    9 |     set<char> charset;
      |         ^~~~
a.cc:12:11: error: 'charset' was not declared in this scope
   12 |           charset.insert(s.at(i));
      |           ^~~~~~~
a.cc:16:19: error: 'charset' was not declared in this scope
   16 |    for(auto itr = charset.begin(); itr != charset.end(); itr++){
      |                   ^~~~~~~
a.cc:20:13: error: 'cout' was not declared in this scope; did you mean 'count'?
   20 |             cout << c << endl;
      |             ^~~~
      |             count
a.cc:20:26: error: 'endl' was not declared in this scope
   20 |             cout << c << endl;
      |                          ^~~~
a.cc:27:4: error: 'cout' was not declared in this scope; did you mean 'count'?
   27 |    cout << "None" << endl;
      |    ^~~~
      |    count
a.cc:27:22: error: 'endl' was not declared in this scope
   27 |    cout << "None" << endl;
      |                      ^~~~
Language: C++

#include<iostream>
#include<string>
using namespace std;
int main() {
	string S;
	cin >> S;
	int x = S.size();
	bool app[26];
	for (int i = 0; i < 26; i++) {
		app[i] = false;

	}
	for (int i = 0; i < x; i++) {
		app[S[i] - 'a'] = ture;
	}
	for (int i = 0, i < 26; i++) {
		if (!app[i]) {
			cout << app[i] << endl;
			return 0;
		}
	}
	cout << "None" << endl;
	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:14:35: error: 'ture' was not declared in this scope
   14 |                 app[S[i] - 'a'] = ture;
      |                                   ^~~~
a.cc:16:26: error: expected ';' before '<' token
   16 |         for (int i = 0, i < 26; i++) {
      |                          ^~
      |                          ;
a.cc:16:27: error: expected primary-expression before '<' token
   16 |         for (int i = 0, i < 26; i++) {
      |                           ^
Language: C++

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

int main(){
    scanf("%s", s);
    bool app[26];
    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;
        }
    }
    puts("None");
    return 0;
}

Compiler output:
a.cc:8:23: warning: multi-character character constant [-Wmultichar]
    8 |     for(int i=0;s[i]!='/0';i++)app[s[i]-'a']=true;
      |                       ^~~~
a.cc: In function 'int main()':
a.cc:5:17: error: 's' was not declared in this scope
    5 |     scanf("%s", s);
      |                 ^
Language: C++

#include <bits/stdc++.h>
using namespace std;
 
int main() {
  string s;
  cin >>s;
  int l  = s.size();
  for(int i =97;i<=122;i++){
    bool c = true;
    char a = i;
    for(int j=0;j<l;j++){
      if(s.at(j) == a){
        c = false;
        break;
    }
    if(c){
      cout << a << endl;
      return 0;
    }
  }
  cout << "None" << endl;
}
        

Compiler output:
a.cc: In function 'int main()':
a.cc:22:2: error: expected '}' at end of input
   22 | }
      |  ^
a.cc:4:12: note: to match this '{'
    4 | int main() {
      |            ^
Language: C++

#include <bits/stdc++.h>
using namespace std;
const int maxx = 1e5 + 7;
char s[maxx];
map <char, bool> vis;
char ans;

int main() {
	scanf("%s", s);
	bool flg = 0;
	for(int i = 0; i < l; i++) vis[s[i]] = 1;
	for(char i = 'a'; i <= 'z'; i++) {
		if(!vis[i]) {
			flg = 1;
			ans = i;
		}
	}
	if(flg) putchar(ans);
	else puts("None");
}

Compiler output:
a.cc: In function 'int main()':
a.cc:11:28: error: 'l' was not declared in this scope
   11 |         for(int i = 0; i < l; i++) vis[s[i]] = 1;
      |                            ^
Language: C++

#include <iostream>
#include <algorithm>
#include <string.h>
using namespace std;
int main(void){
    char s[100005];
    cin>>s;
    bool check[26];
    for(int i=0;i<26;i++){
        check[i]=0;
    }
    int N;
    N=strlen(s);
    int num;
    for(int i=0;i<N;i++){
       num=s[i]-'a';
       check[num]=1;
    }
    int ans=0;
    for(int i=0;i<26;i++){
        if(check[i]==0){
            ans=i+'a';
            break;
        }
    }
    if(ans==0) cout<<"None";
    else
    unsigned char uchar;
    uchar=(char)ans;
    cout<<uchar;
    return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:29:5: error: 'uchar' was not declared in this scope; did you mean 'u_char'?
   29 |     uchar=(char)ans;
      |     ^~~~~
      |     u_char
Language: C++

#include<iostream>
#include<cmath>
#include<algorithm>
#include <cassert>
#include<string>
using namespace std;
int main() {
	int a = 0, b = 0, c = 0, d[100000], e[100000], f = 0, g = 0, h = 0, count = 0;
	char rikka, toka[100000];
	string saya, homu, kyok, mami,mado[100];
	int manji, nk[26] = {false};
	cin >> saya;
	for (int i = 0; i < saya.length(); i++) {
		nk[saya[i]- 'a'] = true;
	}
	for (int k = 0; k < saya.length(); k++) {
		if (nk[k] == false) {
			rikka = 'a' + k;
			cout << rikka << endl;
			return 0;
		}
		if (nk[saya.length - 1] == true) {
			cout << "None" << endl;
		}
	}
	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:22:29: error: invalid use of member function 'std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::size_type std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::length() const [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>; size_type = long unsigned int]' (did you forget the '()' ?)
   22 |                 if (nk[saya.length - 1] == true) {
      |                        ~~~~~^~~~~~
      |                                   ()
Language: C++

#include <iostream>
#include <map>
#include <set>
#include <cmath>
#include <deque>
#include <queue>
#include <stack>
#include <bitset>
#include <string>
#include <vector>
#include <iomanip>
#include <sstream>
#include <utility>
#include <iterator>
#include <algorithm>
#include <functional>
#define rep(i, n) for(int i = 0;i < n;i++)
#define FOR(i, m, n) for(int i = m;i < n;i++)
#define pq priority_queue<int,vector<int>,greater<int>>
#define ll long long
//#define int long long

using namespace std;

typedef pair<int, int> pi;
int n, m, c[26];
string s;
int main() {
	cin >> s;
	rep(i, s.size()) {
		c[s[i] - 'a']++;
	}
	rep(i, 26) {
		if (c[i] == 0) {
			cout << char('a' + i) << endl;
			return 0;
		}
	}
	cout << "None" << endl;
	return 0;
}#include <iostream>
#include <map>
#include <set>
#include <cmath>
#include <deque>
#include <queue>
#include <stack>
#include <bitset>
#include <string>
#include <vector>
#include <iomanip>
#include <sstream>
#include <utility>
#include <iterator>
#include <algorithm>
#include <functional>
#define rep(i, n) for(int i = 0;i < n;i++)
#define FOR(i, m, n) for(int i = m;i < n;i++)
#define pq priority_queue<int,vector<int>,greater<int>>
#define ll long long
//#define int long long

using namespace std;

typedef pair<int, int> pi;
int n, m, c[26];
string s;
int main() {
	cin >> s;
	rep(i, s.size()) {
		c[s[i] - 'a']++;
	}
	rep(i, 26) {
		if (c[i] == 0) {
			cout << char('a' + i) << endl;
			return 0;
		}
	}
	cout << "None" << endl;
	return 0;
}

Compiler output:
a.cc:41:2: error: stray '#' in program
   41 | }#include <iostream>
      |  ^
a.cc:41:3: error: 'include' does not name a type
   41 | }#include <iostream>
      |   ^~~~~~~
a.cc:66:5: error: redefinition of 'int n'
   66 | int n, m, c[26];
      |     ^
a.cc:26:5: note: 'int n' previously declared here
   26 | int n, m, c[26];
      |     ^
a.cc:66:8: error: redefinition of 'int m'
   66 | int n, m, c[26];
      |        ^
a.cc:26:8: note: 'int m' previously declared here
   26 | int n, m, c[26];
      |        ^
a.cc:66:11: error: redefinition of 'int c [26]'
   66 | int n, m, c[26];
      |           ^
a.cc:26:11: note: 'int c [26]' previously declared here
   26 | int n, m, c[26];
      |           ^
a.cc:67:8: error: redefinition of 'std::string s'
   67 | string s;
      |        ^
a.cc:27:8: note: 'std::string s' previously declared here
   27 | string s;
      |        ^
a.cc:68:5: error: redefinition of 'int main()'
   68 | int main() {
      |     ^~~~
a.cc:28:5: note: 'int main()' previously defined here
   28 | int main() {
      |     ^~~~
Language: C++

#include <iostream>
#include <map>
#include <set>
#include <cmath>
#include <deque>
#include <queue>
#include <stack>
#include <bitset>
#include <string>
#include <vector>
#include <iomanip>
#include <sstream>
#include <utility>
#include <iterator>
#include <algorithm>
#include <functional>
#define rep(i, n) for(int i = 0;i < n;i++)
#define FOR(i, m, n) for(int i = m;i < n;i++)
#define pq priority_queue<int,vector<int>,greater<int>>
#define ll long long
//#define int long long

using namespace std;

typedef pair<int, int> pi;
int n, m, c[26];
string s;
void main() {
	cin >> s;
	rep(i, s.size()) {
		c[s[i] - 'a']++;
	}
	rep(i, 26) {
		if (c[i] == 0) {
			cout << char('a' + i) << endl;
			return;
		}
	}
	cout << "None" << endl;
	return;
}

Compiler output:
a.cc:28:1: error: '::main' must return 'int'
   28 | void main() {
      | ^~~~
a.cc: In function 'int main()':
a.cc:36:25: error: return-statement with no value, in function returning 'int' [-fpermissive]
   36 |                         return;
      |                         ^~~~~~
a.cc:40:9: error: return-statement with no value, in function returning 'int' [-fpermissive]
   40 |         return;
      |         ^~~~~~