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

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

int main()
{
	char a[100000];
	int b;
	cin >> a;
	b = strlen(a);
	for (int i = 0; i < b/2+1; i++)
	{
		cout << a[0 + i * 2];
	}
	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:10:13: error: 'strlen' was not declared in this scope
   10 |         b = strlen(a);
      |             ^~~~~~
a.cc:2:1: note: 'strlen' is defined in header '<cstring>'; this is probably fixable by adding '#include <cstring>'
    1 | #include<iostream>
  +++ |+#include <cstring>
    2 | #include<string>
Language: C++

#include <iostream>
#include <algorithm>
#include <cmath>
#include <string>
#include <array>
#include <vector>
#include <functional>
#include <unordered_map>
#include <map>
#include <numeric>
#include <limits>
#include <utility>
#include <queue>
#include <random>
using namespace std;

int main(){
	char s[256];

	cin >> s;

	char a[256];
	int x,i;

	x = strlen(s);

	for (i = 0; i < x; i++) {
		a[i] = s[i * 2];
	}

	cout << a;

	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:25:13: error: 'strlen' was not declared in this scope
   25 |         x = strlen(s);
      |             ^~~~~~
a.cc:15:1: note: 'strlen' is defined in header '<cstring>'; this is probably fixable by adding '#include <cstring>'
   14 | #include <random>
  +++ |+#include <cstring>
   15 | using namespace std;
Language: C++

#include <iostream>
#include <algorithm>
#include <cmath>
#include <string>
#include <array>
#include <vector>
#include <functional>
#include <unordered_map>
#include <map>
#include <numeric>
#include <limits>
#include <utility>
#include <queue>
#include <random>
using namespace std;

int main(){
	char s[100000];

	cin >> s;

	char a[50000];
	int x,i;

	x = strlen(s);

	for (i = 0; i < x; i++) {
		a[i] = s[i * 2];
	}

	cout << a;

	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:25:13: error: 'strlen' was not declared in this scope
   25 |         x = strlen(s);
      |             ^~~~~~
a.cc:15:1: note: 'strlen' is defined in header '<cstring>'; this is probably fixable by adding '#include <cstring>'
   14 | #include <random>
  +++ |+#include <cstring>
   15 | using namespace std;
Language: C++

#include <iostream>
#include <string>

using namespace std;


int main()
{
	string s;

	cin >> s;

	for (int i = 0; i < s.max_size; i = i + 2)
		cout << s[i];
	cout << endl;

	return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:13:31: error: invalid use of member function 'std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::size_type std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::max_size() const [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>; size_type = long unsigned int]' (did you forget the '()' ?)
   13 |         for (int i = 0; i < s.max_size; i = i + 2)
      |                             ~~^~~~~~~~
      |                                       ()
Language: C++

#include <cstdio>
#include <string.h>
#include <cstring>
using namespace std;
string s;
unsigned int i;
int main() {
    scanf("%s", s);
    for (; i <= s.length(); ++i) {
        if (i & 1) {
            putchar(s[i - 1]);
        }
    }
    puts("");
    return 0;
}


Compiler output:
a.cc:5:1: error: 'string' does not name a type; did you mean 'stdin'?
    5 | string s;
      | ^~~~~~
      | stdin
a.cc: In function 'int main()':
a.cc:8:17: error: 's' was not declared in this scope
    8 |     scanf("%s", s);
      |                 ^
Language: C++

#include <cstdio>
#include <string.h>
using namespace std;
string s;
unsigned int i;
int main() {
    scanf("%s", s);
    for (; i <= s.length(); ++i) {
        if (i & 1) {
            putchar(s[i - 1]);
        }
    }
    puts("");
    return 0;
}


Compiler output:
a.cc:4:1: error: 'string' does not name a type; did you mean 'stdin'?
    4 | string s;
      | ^~~~~~
      | stdin
a.cc: In function 'int main()':
a.cc:7:17: error: 's' was not declared in this scope
    7 |     scanf("%s", s);
      |                 ^
Language: C++

#include <cstdio>
using namespace std;
string s;
unsigned int i;
int main() {
    scanf("%s", s);
    for (; i <= s.length(); ++i) {
        if (i & 1) {
            putchar(s[i - 1]);
        }
    }
    puts("");
    return 0;
}


Compiler output:
a.cc:3:1: error: 'string' does not name a type; did you mean 'stdin'?
    3 | string s;
      | ^~~~~~
      | stdin
a.cc: In function 'int main()':
a.cc:6:17: error: 's' was not declared in this scope
    6 |     scanf("%s", s);
      |                 ^
Language: C++

#include<iostream>
#include<string>
using namespace std;
int main () {
  string s;
  cin >> s;
  string t[5100];
  int n = (s.size() + 1) / 2;
  for (int i = 0, i < n, i ++) {
    t[i] = s[2 * i];
  }
  cout << t << endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:9:20: error: expected ';' before '<' token
    9 |   for (int i = 0, i < n, i ++) {
      |                    ^~
      |                    ;
a.cc:9:21: error: expected primary-expression before '<' token
    9 |   for (int i = 0, i < n, i ++) {
      |                     ^
a.cc:9:30: error: expected ';' before ')' token
    9 |   for (int i = 0, i < n, i ++) {
      |                              ^
      |                              ;
Language: C++

#include<bits/stdc++.h>
using namespace std;
int main(){
    char str[100010];
    cin>>str+1;
    int len=strlen(str+1);
    for(int i=1;i<=len;i+=2){
        cout<<str[i];
    }


Compiler output:
a.cc: In function 'int main()':
a.cc:9:6: error: expected '}' at end of input
    9 |     }
      |      ^
a.cc:3:11: note: to match this '{'
    3 | int main(){
      |           ^
Language: C

include <stdio.h>
int main(){
  char a[100];
  scanf("%s",a);
  for(int i=0;i<100;i++){
    if((i+1)%2==1)printf("%c",a[i]);
    if(a[i]=='\0')break;
  }
  printf("\n");
  return 0;
}

Compiler output:
main.c:1:9: error: expected '=', ',', ';', 'asm' or '__attribute__' before '<' token
    1 | include <stdio.h>
      |         ^
Language: C++

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

int main(){
  string s,a;
  a="";
  cin >> s;
  for(int i=0;i<s.size;i++){
    if(i%2==0){
      a+=s.at(i);
    }
  }
  cout << a << endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:9:19: error: invalid use of member function 'std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::size_type std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::size() const [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>; size_type = long unsigned int]' (did you forget the '()' ?)
    9 |   for(int i=0;i<s.size;i++){
      |                 ~~^~~~
      |                       ()
Language: C++

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

int main(){
  string s;
  cin >> s;
  int size = s.size();
  char copy[size / 2];
  int counter = 0;
  for(int i = 0; i < size; i += 2){
    copy[c] = s[i];
    c++;
  }
  cout << copy << endl;
  return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:11:10: error: 'c' was not declared in this scope
   11 |     copy[c] = s[i];
      |          ^
Language: C++

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

int main(){
  string s;
  cin >> s;
  int size = s.size();
  string copy[size];
  int counter = 0;
  for(int i = 0; i < size; i += 2){
    copy[c] = s[i];
    c++;
  }
  cout << copy << endl;
  return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:11:10: error: 'c' was not declared in this scope
   11 |     copy[c] = s[i];
      |          ^
Language: C++

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

int main(){
 string s;
 cin >> s;
 for(int i = 0; i < N;i++) if(i % 2 != 0) cout << s
 
}


Compiler output:
a.cc: In function 'int main()':
a.cc:9:21: error: 'N' was not declared in this scope
    9 |  for(int i = 0; i < N;i++) if(i % 2 != 0) cout << s
      |                     ^
a.cc:9:52: error: expected ';' before '}' token
    9 |  for(int i = 0; i < N;i++) if(i % 2 != 0) cout << s
      |                                                    ^
      |                                                    ;
   10 | 
   11 | }
      | ~
Language: C++

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

int main() {
	char s[10000];
	gets(s);
	for(int i=0;i<strlen(s);i++){
		if(i%2==0){
			printf("%c",s[i]);
		}
	}
	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:7:9: error: 'gets' was not declared in this scope; did you mean 'getw'?
    7 |         gets(s);
      |         ^~~~
      |         getw
Language: C++

#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
using namespace std;
int main() {
	char s[10000];
	gets(s);
	for(int i=0;i<strlen(s);i++){
		if(i%2==0){
			printf("%c",s[i]);
		}
	}
	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:8:9: error: 'gets' was not declared in this scope; did you mean 'getw'?
    8 |         gets(s);
      |         ^~~~
      |         getw
Language: C++

#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
using namespace std;
int main(int argc, char** argv) {
	char s[10000];
	gets(s);
	for(int i=0;i<strlen(s);i++){
		if(i%2==0){
			printf("%c",s[i]);
		}
	}
	return 0;
}

Compiler output:
a.cc: In function 'int main(int, char**)':
a.cc:8:9: error: 'gets' was not declared in this scope; did you mean 'getw'?
    8 |         gets(s);
      |         ^~~~
      |         getw
Language: C++

#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
/* run this program using the console pauser or add your own getch, system("pause") or input loop */

int main(int argc, char** argv) {
	char s[10000];
	gets(s);
	for(int i=0;i<strlen(s);i++){
		if(i%2==0){
			printf("%c",s[i]);
		}
	}
	return 0;
}

Compiler output:
a.cc: In function 'int main(int, char**)':
a.cc:9:9: error: 'gets' was not declared in this scope; did you mean 'getw'?
    9 |         gets(s);
      |         ^~~~
      |         getw
Language: C++


using namespace std;


int main(){
  string s;
  cin >> s;
  int N = s.size();
  string ans;
  for (int i=0;i<N;i+=2) ans += s[i];
  cout << ans <<endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:6:3: error: 'string' was not declared in this scope
    6 |   string s;
      |   ^~~~~~
a.cc:1:1: note: 'std::string' is defined in header '<string>'; this is probably fixable by adding '#include <string>'
  +++ |+#include <string>
    1 | 
a.cc:7:3: error: 'cin' was not declared in this scope
    7 |   cin >> s;
      |   ^~~
a.cc:1:1: note: 'std::cin' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
  +++ |+#include <iostream>
    1 | 
a.cc:7:10: error: 's' was not declared in this scope
    7 |   cin >> s;
      |          ^
a.cc:9:9: error: expected ';' before 'ans'
    9 |   string ans;
      |         ^~~~
      |         ;
a.cc:10:26: error: 'ans' was not declared in this scope
   10 |   for (int i=0;i<N;i+=2) ans += s[i];
      |                          ^~~
a.cc:11:3: error: 'cout' was not declared in this scope
   11 |   cout << ans <<endl;
      |   ^~~~
a.cc:11:3: note: 'std::cout' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
a.cc:11:11: error: 'ans' was not declared in this scope
   11 |   cout << ans <<endl;
      |           ^~~
a.cc:11:17: error: 'endl' was not declared in this scope
   11 |   cout << ans <<endl;
      |                 ^~~~
a.cc:1:1: note: 'std::endl' is defined in header '<ostream>'; this is probably fixable by adding '#include <ostream>'
  +++ |+#include <ostream>
    1 |
Language: C++

#include <iostream>

int main(){
  string s;
  cin >> s;
  int N = s.size();
  string ans;
  for (int i=0;i<N;i+=2) ans += s[i];
  cout << ans <<endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:4:3: error: 'string' was not declared in this scope
    4 |   string s;
      |   ^~~~~~
a.cc:4:3: 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:5:3: error: 'cin' was not declared in this scope; did you mean 'std::cin'?
    5 |   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:5:10: error: 's' was not declared in this scope
    5 |   cin >> s;
      |          ^
a.cc:7:9: error: expected ';' before 'ans'
    7 |   string ans;
      |         ^~~~
      |         ;
a.cc:8:26: error: 'ans' was not declared in this scope; did you mean 'abs'?
    8 |   for (int i=0;i<N;i+=2) ans += s[i];
      |                          ^~~
      |                          abs
a.cc:9:3: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
    9 |   cout << ans <<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:9:11: error: 'ans' was not declared in this scope; did you mean 'abs'?
    9 |   cout << ans <<endl;
      |           ^~~
      |           abs
a.cc:9:17: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
    9 |   cout << ans <<endl;
      |                 ^~~~
      |                 std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~
Language: C++

int main(){
  string s;
  cin >> s;
  int N = s.size();
  string ans;
  for (int i=0;i<N;i+=2) ans += s[i];
  cout << ans <<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:5:9: error: expected ';' before 'ans'
    5 |   string ans;
      |         ^~~~
      |         ;
a.cc:6:26: error: 'ans' was not declared in this scope
    6 |   for (int i=0;i<N;i+=2) ans += s[i];
      |                          ^~~
a.cc:7:3: error: 'cout' was not declared in this scope
    7 |   cout << ans <<endl;
      |   ^~~~
a.cc:7:11: error: 'ans' was not declared in this scope
    7 |   cout << ans <<endl;
      |           ^~~
a.cc:7:17: error: 'endl' was not declared in this scope
    7 |   cout << ans <<endl;
      |                 ^~~~
Language: C++

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

int main() {
  
	std::string str;
	cin >> str;

  int N = strlen(str);
  int a =N - N/2 - N%2;
  for (int i = 0; i < a; ++i){
    str.erase(str.begin() + i);
  }
    cout << str <<endl;
}



Compiler output:
a.cc: In function 'int main()':
a.cc:10:11: error: 'strlen' was not declared in this scope
   10 |   int N = strlen(str);
      |           ^~~~~~
a.cc:2:1: note: 'strlen' is defined in header '<cstring>'; this is probably fixable by adding '#include <cstring>'
    1 | #include<iostream>
  +++ |+#include <cstring>
    2 | # include <string>
Language: C++

#include<iostream>
#include<string>
using namespace std;
int main(){
    string s;
    cin >> s;
    string s2;
    int i;
    int t = 2 * i ;
    int ss =s.size()/2
    for (i = 0; i<= ss;i++){
        s2[i] = s[t];
    }
    cout << s2 << endl;
    return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:11:5: error: expected ',' or ';' before 'for'
   11 |     for (i = 0; i<= ss;i++){
      |     ^~~
a.cc:11:27: error: expected ';' before ')' token
   11 |     for (i = 0; i<= ss;i++){
      |                           ^
      |                           ;
Language: C++

#include<iostream>
#include<string>
using namespace std;
int main(){
    string s;
    cin >> s;
    string s2;
    int i;
    int t = 2*i-1
    for (i = 0;t< s.size();i++){
        s2[i] = s[t];
    }
    cout << s2 << endl;
    return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:10:5: error: expected ',' or ';' before 'for'
   10 |     for (i = 0;t< s.size();i++){
      |     ^~~
a.cc:10:31: error: expected ';' before ')' token
   10 |     for (i = 0;t< s.size();i++){
      |                               ^
      |                               ;
Language: C++

#include <bits/stdc++.h>

#define o(output) cout << output << endl;

using namespace std;

string s,t;
int a,b,c,d;

int main(){
  cin >>s;
  for(int i=0;i<s.size();i+=2)t+=a[i];
  cout<<t<<endl;
  }

Compiler output:
a.cc: In function 'int main()':
a.cc:12:35: error: invalid types 'int[int]' for array subscript
   12 |   for(int i=0;i<s.size();i+=2)t+=a[i];
      |                                   ^
Language: C++

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

int main() {
    string s;
    cin >> s;
    vector<char> result;
    for(int i=0;i<s.size();i++){
        if(i%2 ==0) result.push_back(s[i]);
    }
    for_each(result.begin(), result.end(), [](char x){
        cout << x;
    });
    cout << endl;
    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:12:5: error: 'for_each' was not declared in this scope
   12 |     for_each(result.begin(), result.end(), [](char x){
      |     ^~~~~~~~
Language: C++

#include <iostream>
using namespace std;

int main(){
	string s;
	cin >> s;
	for(i=0; i<s.size(), i+=2) cout << s[i];
}

Compiler output:
a.cc: In function 'int main()':
a.cc:7:13: error: 'i' was not declared in this scope
    7 |         for(i=0; i<s.size(), i+=2) cout << s[i];
      |             ^
a.cc:7:34: error: expected ';' before ')' token
    7 |         for(i=0; i<s.size(), i+=2) cout << s[i];
      |                                  ^
      |                                  ;
Language: C++

#include 
#include 
using namespace std;

int main()
{
	string s;
	cin >> s;
	for(int i = 0;i < s.size();i += 2)
	{
		cout << s[i];
	}
	cout << endl;
	return 0;

}

Compiler output:
a.cc:1:10: error: #include expects "FILENAME" or <FILENAME>
    1 | #include
      |          ^
a.cc:2:10: error: #include expects "FILENAME" or <FILENAME>
    2 | #include
      |          ^
a.cc: In function 'int main()':
a.cc:7:9: error: 'string' was not declared in this scope
    7 |         string s;
      |         ^~~~~~
a.cc:1:1: note: 'std::string' is defined in header '<string>'; this is probably fixable by adding '#include <string>'
  +++ |+#include <string>
    1 | #include
a.cc:8:9: error: 'cin' was not declared in this scope
    8 |         cin >> s;
      |         ^~~
a.cc:1:1: note: 'std::cin' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
  +++ |+#include <iostream>
    1 | #include
a.cc:8:16: error: 's' was not declared in this scope
    8 |         cin >> s;
      |                ^
a.cc:11:17: error: 'cout' was not declared in this scope
   11 |                 cout << s[i];
      |                 ^~~~
a.cc:11:17: note: 'std::cout' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
a.cc:13:9: error: 'cout' was not declared in this scope
   13 |         cout << endl;
      |         ^~~~
a.cc:13:9: note: 'std::cout' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
a.cc:13:17: error: 'endl' was not declared in this scope
   13 |         cout << endl;
      |                 ^~~~
a.cc:1:1: note: 'std::endl' is defined in header '<ostream>'; this is probably fixable by adding '#include <ostream>'
  +++ |+#include <ostream>
    1 | #include
Language: C++

#include<stdio.h>

int main() {
	char s[100000];
	scanf("%s", s);
	int i = 0;
	while(s[i]!='\0'){
		if (i % 2 == 0) {
			printf("%s", s[i]);
		}
		i++
	}
	printf("\n");
	
	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:11:20: error: expected ';' before '}' token
   11 |                 i++
      |                    ^
      |                    ;
   12 |         }
      |         ~
Language: C++

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

int main() {

	string txt;
	cin >> txt;
	int len = 0;

	len = strlen(txt.c_str());
	//cout << len;

	string str(txt);
	for (int i = 0; i < len; i++)
	{
		double amari = i % 2;
		if (amari == 0.0){
			cout << str[i];
		}
	}
}

Compiler output:
a.cc: In function 'int main()':
a.cc:11:15: error: 'strlen' was not declared in this scope
   11 |         len = strlen(txt.c_str());
      |               ^~~~~~
a.cc:2:1: note: 'strlen' is defined in header '<cstring>'; this is probably fixable by adding '#include <cstring>'
    1 | #include <iostream>
  +++ |+#include <cstring>
    2 | #include <string>
Language: C++

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

int main() {

	string txt;
	cin >> txt;
	int len;

	len = strlen(txt.c_str());
	//cout << len;

	string str(txt);
	for (int i = 0; i < len; i++)
	{
		double amari = i % 2;
		if (amari == 0.0){
			cout << str[i];
		}
	}
}

Compiler output:
a.cc: In function 'int main()':
a.cc:11:15: error: 'strlen' was not declared in this scope
   11 |         len = strlen(txt.c_str());
      |               ^~~~~~
a.cc:2:1: note: 'strlen' is defined in header '<cstring>'; this is probably fixable by adding '#include <cstring>'
    1 | #include <iostream>
  +++ |+#include <cstring>
    2 | #include <string>
Language: C

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

int main() {
	char s[100010];
	scanf("%s",s);
	long long int i=0;
	while(s[i]!='\n'){
		if(i%2==0){
			printf("%c",s[i]);
		}
		i++;
	}
	printf("\n");
	return 0;
}

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

int main() {
	char s[100010];
	scanf("%s",s);
	long long int i=0;
	while(s[i]!='\n'){
		if(i%2==0){
			printf("%c",s[i]);
		}
		i++;
	}
	printf("\n");
	return 0;
}



Compiler output:
main.c:23:5: error: redefinition of 'main'
   23 | int main() {
      |     ^~~~
main.c:5:5: note: previous definition of 'main' with type 'int()'
    5 | int main() {
      |     ^~~~
Language: C++

#include <iostream>
#include <stdio.h>
#include <cstring>
#include <algorithm>
#include <string>
#include <math.h>
#include <cstdlib>
#include <vector>
#include <queue>
#include <set>
using namespace std;

int main(){
	char[1000000];
	for(int i=0;i<1000000;i++)cin>>char[i];
	for(int i=0;i<200000;i++) cout<<char[2*i]; 
}

Compiler output:
a.cc: In function 'int main()':
a.cc:14:14: error: expected identifier before numeric constant
   14 |         char[1000000];
      |              ^~~~~~~
a.cc:14:14: error: expected ']' before numeric constant
   14 |         char[1000000];
      |              ^~~~~~~
      |              ]
a.cc:14:13: error: structured binding declaration cannot have type 'char'
   14 |         char[1000000];
      |             ^
a.cc:14:13: note: type must be cv-qualified 'auto' or reference to cv-qualified 'auto'
a.cc:14:13: error: empty structured binding declaration
a.cc:14:22: error: expected initializer before ';' token
   14 |         char[1000000];
      |                      ^
a.cc:15:40: error: expected primary-expression before 'char'
   15 |         for(int i=0;i<1000000;i++)cin>>char[i];
      |                                        ^~~~
a.cc:16:41: error: expected primary-expression before 'char'
   16 |         for(int i=0;i<200000;i++) cout<<char[2*i];
      |                                         ^~~~
Language: C

#include<stdio.h>
#include<string.h>
int main()
{
	int i;
	char str1[20],str2[20];
    gets(str1);
	for(i=0;str1[i];i++)
	{
	    	if(i%2)str2[i]=str1[i/2];
    }
     	str2[i]=0;
	    printf("%s\n",str2);
	}

}


Compiler output:
main.c: In function 'main':
main.c:7:5: error: implicit declaration of function 'gets'; did you mean 'fgets'? [-Wimplicit-function-declaration]
    7 |     gets(str1);
      |     ^~~~
      |     fgets
main.c: At top level:
main.c:16:1: error: expected identifier or '(' before '}' token
   16 | }
      | ^
Language: C++

import java.util.*;
 
public class Main {
	public static void main(String[] args) {
		Scanner scanner = new Scanner(System.in);
		String str = scanner.nextLine();

        for(int i = 0; i <= str.length(); i += 2){
            System.out.print(str.substring(i,i+1));
        }
        System.out.println();
	}
}

Compiler output:
a.cc:1:1: error: 'import' does not name a type
    1 | import java.util.*;
      | ^~~~~~
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 a[100],q[100];
	int i=0,b;
	while (1)
	{
		int c=0;
		gets(a);
		for (i=0;i<strlen(a);i++)
		{
            q[i]=a[2*i];
			c=i;
			
		}
		if (c%2==0)
		{
		  q[c-1]='\0';
		}
		else 
		{
			q[c]='\0';
		}
		puts(q);
	}

	return 0;

}

Compiler output:
a.cc: In function 'int main()':
a.cc:10:17: error: 'gets' was not declared in this scope; did you mean 'getw'?
   10 |                 gets(a);
      |                 ^~~~
      |                 getw
Language: C++

>#include<iostream>
>#include<string>
>#include<algorithm>
>using namespace std;
>int main(){
>	string s;
>	cin>>s;
>	for(int i=0;i<s.size();i++){
>		if(i%2==0){
>			cout<<s[i];
>			
>		}
>	}
>	cout<<endl;
>}

Compiler output:
a.cc:1:2: error: stray '#' in program
    1 | >#include<iostream>
      |  ^
a.cc:2:2: error: stray '#' in program
    2 | >#include<string>
      |  ^
a.cc:3:2: error: stray '#' in program
    3 | >#include<algorithm>
      |  ^
a.cc:1:1: error: expected unqualified-id before '>' token
    1 | >#include<iostream>
      | ^
a.cc:5:1: error: expected unqualified-id before '>' token
    5 | >int main(){
      | ^
Language: C++

#include<iostream>
#include<string.h>

using namespace std;

int main(){
    string s;
    int n;
    cin>>s;
    n=s.length();
    for(int i=0;i<n;i++){
        if(i%2==0)cout<<s[i];
    }cout<<endl:
}

Compiler output:
a.cc: In function 'int main()':
a.cc:13:16: error: expected ';' before ':' token
   13 |     }cout<<endl:
      |                ^
      |                ;
Language: C

#include <stdio.h>
int main(void)
{
  int x,t;
  char s[100004]={0};
  scanf("%s",s);
  x=(1+strlen(s))/2+1
  for(t=0;t<x;++t){
    s[t]=s[2*t];
  }
  printf("%s\n", s);
  return 0;
}


Compiler output:
main.c: In function 'main':
main.c:7:8: error: implicit declaration of function 'strlen' [-Wimplicit-function-declaration]
    7 |   x=(1+strlen(s))/2+1
      |        ^~~~~~
main.c:2:1: note: include '<string.h>' or provide a declaration of 'strlen'
    1 | #include <stdio.h>
  +++ |+#include <string.h>
    2 | int main(void)
main.c:7:8: warning: incompatible implicit declaration of built-in function 'strlen' [-Wbuiltin-declaration-mismatch]
    7 |   x=(1+strlen(s))/2+1
      |        ^~~~~~
main.c:7:8: note: include '<string.h>' or provide a declaration of 'strlen'
main.c:7:22: error: expected ';' before 'for'
    7 |   x=(1+strlen(s))/2+1
      |                      ^
      |                      ;
    8 |   for(t=0;t<x;++t){
      |   ~~~
Language: C++

#include <cstdio>
#include <cstring>
#include <iostream>
using namespace std;
typedef long long LL;
const int MAxn = 2e5 + 5;
const int MA_N = 5e3 + 5;

int vis[MAxn] = {0};

int main(){
	int n, m;
	char s[MAxn];
	gets(s+1);
	int len = strlen(s + 1);
	for (int i = 1; i <= len; i++)
		if(i%2) printf("%c", s[i]);
	printf("\n");
	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:14:9: error: 'gets' was not declared in this scope; did you mean 'getw'?
   14 |         gets(s+1);
      |         ^~~~
      |         getw
Language: C++

#include <iostream>
using namespace std;

char s[100005];

int main()
{
	cin >> s;
	int len = strlen(s);
	for (int i = 0; i < len; i+= 2)
		cout << s[i];
	cout << endl;
	return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:9:19: error: 'strlen' was not declared in this scope
    9 |         int len = strlen(s);
      |                   ^~~~~~
a.cc:2:1: note: 'strlen' is defined in header '<cstring>'; this is probably fixable by adding '#include <cstring>'
    1 | #include <iostream>
  +++ |+#include <cstring>
    2 | using namespace std;
Language: C++

#include <iostream>
#include <algorithm>
#include <string>
 using namespace std;
 
 
 
 int main(){
    string s;
    cin>>s;
    int i;
    for(i=1;i<s.length;i+=2){
    cout<<s[i];
    }
    cout<<endl;
    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:12:17: 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 '()' ?)
   12 |     for(i=1;i<s.length;i+=2){
      |               ~~^~~~~~
      |                       ()
Language: C++

#include "stdafx.h"
#include<iostream>
#include<string>
#include<algorithm>

typedef long long ll;
using namespace std;
int main()
{
	string b;
	cin >> b;
	for (size_t i = 0; i < b.size(); i++)
	{
		if (i % 2 == 0)
		{
			cout << b[i];
		}
	}
}

Compiler output:
a.cc:1:10: fatal error: stdafx.h: No such file or directory
    1 | #include "stdafx.h"
      |          ^~~~~~~~~~
compilation terminated.
Language: C++

/*
#include <iostream>
#include <algorithm>
#include <cstdio>
#include <cmath>
#include <string>
#include <cctype>
#include <stack>
#include <queue>
#include <vector>
#include <cstdlib>
#include <list>
#include <cmath>
#include <map>
#include <utility>
#include <numeric>
#include <set>
#include <map>
#include <functional>
*/

#include "Header1.h"

#define _USE_MATH_DEFINES

using namespace std;
using ll = long long;
using P = pair<int, int>;

const ll INF = 999999999;
const ll atcoder = 1000000007;
const int dx[4] = { 1 , 0 , -1 ,0 };
const int dy[4] = { 0 , 1 , 0 , -1 };

int d[1000][1000];

void Daijkstra() { //単一始点最短経路

	priority_queue< P, vector<P>, greater<P> > Q;


}

void Warshall(){ //全点対最短経路 O(V^3)

	int n, m;
	cin >> n >> m;

	for (int i = 0; i < n; i++) {
		for (int j = 0; j < n; j++) {
			d[i][j] = INF;
		}
	}

	for (int i = 0; i < m; i++) {//m : 節の数
		int a, b, t;
		cin >> a >> b >> t;
		d[a - 1][b - 1] = d[b - 1][a - 1] = t;
	}

	for (int k = 0; k < n; k++) { //n : 頂点数
		for (int i = 0; i < n; i++) {
			for (int j = 0; j < n; j++) {
				d[i][j] = min(d[i][j], d[i][k] + d[k][j]);
			}
		}
	}
}


int main() {

	string s;
	cin >> s;

	for (int i = 0; i < s.length(); i += 2)
		cout << s[i];
	cout << endl;
	

	return 0;

}

Compiler output:
a.cc:22:10: fatal error: Header1.h: No such file or directory
   22 | #include "Header1.h"
      |          ^~~~~~~~~~~
compilation terminated.
Language: C

#include <stdio.h>
#define MAX_NUM 100000

int main(void){
	char S[MAX_NUM+1] = {'\0'};
	int i;

	scanf("%s", S);
	for(i=0; i<MAX_NUM; i++){
		if(i%2 == 0){
			pritf("%c", S[i]);
		}
	}

	return 0;
}

Compiler output:
main.c: In function 'main':
main.c:11:25: error: implicit declaration of function 'pritf'; did you mean 'printf'? [-Wimplicit-function-declaration]
   11 |                         pritf("%c", S[i]);
      |                         ^~~~~
      |                         printf
Language: C++

#include<bits/stdc++.h>
using namespace std;
int main()
{
  string s;
  cin>>s;
  string oup=s[0];
  for(int i=1;i<s.length();i++)
  {
    if((i+1)%2!=0)
      oup+=s[i];
  }
  cout<<oup<<"\n";
}

Compiler output:
a.cc: In function 'int main()':
a.cc:7:17: error: conversion from '__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type' {aka 'char'} to non-scalar type 'std::string' {aka 'std::__cxx11::basic_string<char>'} requested
    7 |   string oup=s[0];
      |                 ^
Language: C++

#include <bits/stdc++.h>

int main() {
  std::string str;
  std::cin >> str;
  std::queue<std::basic_string<char>> kisu;
  for(int a = 0; a < (int)str.size(); a = a + 2) {
    kisu.push(str[a]);
  }
  while(!kisu.empty()) {
    std::cout << kisu.front() << std::endl;
    kisu.pop();
  }
}

Compiler output:
a.cc: In function 'int main()':
a.cc:8:14: error: no matching function for call to 'std::queue<std::__cxx11::basic_string<char> >::push(__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type&)'
    8 |     kisu.push(str[a]);
      |     ~~~~~~~~~^~~~~~~~
In file included from /usr/include/c++/14/queue:66,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:157,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_queue.h:283:7: note: candidate: 'void std::queue<_Tp, _Sequence>::push(const value_type&) [with _Tp = std::__cxx11::basic_string<char>; _Sequence = std::deque<std::__cxx11::basic_string<char>, std::allocator<std::__cxx11::basic_string<char> > >; value_type = std::__cxx11::basic_string<char>]'
  283 |       push(const value_type& __x)
      |       ^~~~
/usr/include/c++/14/bits/stl_queue.h:283:30: note:   no known conversion for argument 1 from '__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type' {aka 'char'} to 'const std::queue<std::__cxx11::basic_string<char> >::value_type&' {aka 'const std::__cxx11::basic_string<char>&'}
  283 |       push(const value_type& __x)
      |            ~~~~~~~~~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_queue.h:288:7: note: candidate: 'void std::queue<_Tp, _Sequence>::push(value_type&&) [with _Tp = std::__cxx11::basic_string<char>; _Sequence = std::deque<std::__cxx11::basic_string<char>, std::allocator<std::__cxx11::basic_string<char> > >; value_type = std::__cxx11::basic_string<char>]'
  288 |       push(value_type&& __x)
      |       ^~~~
/usr/include/c++/14/bits/stl_queue.h:288:25: note:   no known conversion for argument 1 from '__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type' {aka 'char'} to 'std::queue<std::__cxx11::basic_string<char> >::value_type&&' {aka 'std::__cxx11::basic_string<char>&&'}
  288 |       push(value_type&& __x)
      |            ~~~~~~~~~~~~~^~~
Language: C++

#include <bits/stdc++.h>

int main() {
  std::string str;
  std::cin >> str;
  std::queue<std::string> kisu;
  for(int a = 0; a < (int)str.size(); a = a + 2) {
    kisu.push(str[a]);
  }
  while(!kisu.empty()) {
    std::cout << kisu.front() << std::endl;
    kisu.pop();
  }
}

Compiler output:
a.cc: In function 'int main()':
a.cc:8:14: error: no matching function for call to 'std::queue<std::__cxx11::basic_string<char> >::push(__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type&)'
    8 |     kisu.push(str[a]);
      |     ~~~~~~~~~^~~~~~~~
In file included from /usr/include/c++/14/queue:66,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:157,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_queue.h:283:7: note: candidate: 'void std::queue<_Tp, _Sequence>::push(const value_type&) [with _Tp = std::__cxx11::basic_string<char>; _Sequence = std::deque<std::__cxx11::basic_string<char>, std::allocator<std::__cxx11::basic_string<char> > >; value_type = std::__cxx11::basic_string<char>]'
  283 |       push(const value_type& __x)
      |       ^~~~
/usr/include/c++/14/bits/stl_queue.h:283:30: note:   no known conversion for argument 1 from '__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type' {aka 'char'} to 'const std::queue<std::__cxx11::basic_string<char> >::value_type&' {aka 'const std::__cxx11::basic_string<char>&'}
  283 |       push(const value_type& __x)
      |            ~~~~~~~~~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_queue.h:288:7: note: candidate: 'void std::queue<_Tp, _Sequence>::push(value_type&&) [with _Tp = std::__cxx11::basic_string<char>; _Sequence = std::deque<std::__cxx11::basic_string<char>, std::allocator<std::__cxx11::basic_string<char> > >; value_type = std::__cxx11::basic_string<char>]'
  288 |       push(value_type&& __x)
      |       ^~~~
/usr/include/c++/14/bits/stl_queue.h:288:25: note:   no known conversion for argument 1 from '__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type' {aka 'char'} to 'std::queue<std::__cxx11::basic_string<char> >::value_type&&' {aka 'std::__cxx11::basic_string<char>&&'}
  288 |       push(value_type&& __x)
      |            ~~~~~~~~~~~~~^~~
Language: C++

#include <bits/stdc++.h>

int main() {
  std::string str;
  std::cin >> str;
  std::queue<std::string> kisu;
  for(int a = 0; a < (int)str.size(); a = a + 2;) {
    kisu.push(str[a]);
  }
  while(!kisu.empty()) {
    std::cout << kisu.front() << std::endl;
    kisu.pop();
  }
}

Compiler output:
a.cc: In function 'int main()':
a.cc:7:48: error: expected ')' before ';' token
    7 |   for(int a = 0; a < (int)str.size(); a = a + 2;) {
      |      ~                                         ^
      |                                                )
a.cc:7:49: error: expected primary-expression before ')' token
    7 |   for(int a = 0; a < (int)str.size(); a = a + 2;) {
      |                                                 ^
Language: Java

import java.util.*;
import java.math.*;
import java.io.*;


public class code {
    public static void main(String args[]){
        Scanner sc = new Scanner(System.in);
        String s = sc.next();
        for(int i = 0 ; i < s.length() ; i ++){
            if(i % 2 == 0){
                System.out.print(s.charAt(i));
            }
        }
    }
}

Compiler output:
Main.java:6: error: class code is public, should be declared in a file named code.java
public class code {
       ^
1 error
Language: C++

#include <iostream>	
#include <string>
#include <algorithm>
#include <vector>
#include <list>
using namespace std;
typedef unsigned long long LL
int main() {

	string s;
	cin >> s;
	LL len = s.length();

	if (len % 2 != 0) {
		//奇数
		for (unsigned int i = 0; i < ((len + 1) / 2); i++)
		{
			cout << s[i * 2];
		}
	}
	else {
		for (unsigned int i = 0; i <= (len / 2); i++)
		{
			cout << s[i * 2];
		}
	}
	cout << endl;
}

Compiler output:
a.cc:8:1: error: expected initializer before 'int'
    8 | int main() {
      | ^~~
Language: C++

#include<iostream>

using namespace std;
int main()
{
    string s;
    string r("");
    cin >> s;

    int i;

    for (i = 0; i < s.size(); i++) {
        if i % 2 == 0 {
            r += s[i];
        }
    }
    cout << r << endl;
    return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:13:12: error: expected '(' before 'i'
   13 |         if i % 2 == 0 {
      |            ^
      |            (
Language: C++

#include <cstdio>

int main()
{
    char data[100010];
    char result[100010];
    scanf_s("%s", buf);
    
    len = strlen(data);
    for (int i = 0; i < len; i+=2)
    {
       result[i>>1] = data[i];
    }

    printf("%s", result);
    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:7:19: error: 'buf' was not declared in this scope
    7 |     scanf_s("%s", buf);
      |                   ^~~
a.cc:7:5: error: 'scanf_s' was not declared in this scope; did you mean 'scanf'?
    7 |     scanf_s("%s", buf);
      |     ^~~~~~~
      |     scanf
a.cc:9:5: error: 'len' was not declared in this scope
    9 |     len = strlen(data);
      |     ^~~
a.cc:9:11: error: 'strlen' was not declared in this scope
    9 |     len = strlen(data);
      |           ^~~~~~
a.cc:2:1: note: 'strlen' is defined in header '<cstring>'; this is probably fixable by adding '#include <cstring>'
    1 | #include <cstdio>
  +++ |+#include <cstring>
    2 |
Language: C

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

int main(void)
{
        char str[255]={0};
        int i,len;
        char ans[255]={0};

        scanf("%s",str);
        len=strlen(str);
        for(i=0;i<len;i+=2) {
                ans[j++]=str[i];
                j++;
        }
        printf("%s",ans);

        return 0;
}

Compiler output:
main.c: In function 'main':
main.c:13:21: error: 'j' undeclared (first use in this function)
   13 |                 ans[j++]=str[i];
      |                     ^
main.c:13:21: note: each undeclared identifier is reported only once for each function it appears in
Language: C

int main(void)
{
        char str[255]={0};
        int i,len;
        char ans[255]={0};

        len=strlen(str);
        scanf("%s",str);
        for(i=0;i<len;i+=2) {
                ans[j++]=str[i];
                j++;
        }
        printf("%s",ans);

        return 0;
}

Compiler output:
main.c: In function 'main':
main.c:7:13: error: implicit declaration of function 'strlen' [-Wimplicit-function-declaration]
    7 |         len=strlen(str);
      |             ^~~~~~
main.c:1:1: note: include '<string.h>' or provide a declaration of 'strlen'
  +++ |+#include <string.h>
    1 | int main(void)
main.c:7:13: warning: incompatible implicit declaration of built-in function 'strlen' [-Wbuiltin-declaration-mismatch]
    7 |         len=strlen(str);
      |             ^~~~~~
main.c:7:13: note: include '<string.h>' or provide a declaration of 'strlen'
main.c:8:9: error: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
    8 |         scanf("%s",str);
      |         ^~~~~
main.c:1:1: note: include '<stdio.h>' or provide a declaration of 'scanf'
  +++ |+#include <stdio.h>
    1 | int main(void)
main.c:8:9: warning: incompatible implicit declaration of built-in function 'scanf' [-Wbuiltin-declaration-mismatch]
    8 |         scanf("%s",str);
      |         ^~~~~
main.c:8:9: note: include '<stdio.h>' or provide a declaration of 'scanf'
main.c:10:21: error: 'j' undeclared (first use in this function)
   10 |                 ans[j++]=str[i];
      |                     ^
main.c:10:21: note: each undeclared identifier is reported only once for each function it appears in
main.c:13:9: error: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
   13 |         printf("%s",ans);
      |         ^~~~~~
main.c:13:9: note: include '<stdio.h>' or provide a declaration of 'printf'
main.c:13:9: warning: incompatible implicit declaration of built-in function 'printf' [-Wbuiltin-declaration-mismatch]
main.c:13:9: note: include '<stdio.h>' or provide a declaration of 'printf'
Language: C

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


void oddString(char *s,char *c){
    int i,j=1;
    c[0]=s[0];
    for(i=1;i<strlen(s);i++){
        if(s[i]%2==0){
            c[j++] = s[i];
        }
    }
}

int main(void){
    char str1[100]={0},str2[100]={0};
    scanf("%s"str);
    oddString(str1,str2);
    printf("%s",str2);
    return 0;
}

Compiler output:
main.c: In function 'main':
main.c:17:15: error: expected ')' before 'str'
   17 |     scanf("%s"str);
      |          ~    ^~~
      |               )
Language: C++

#include<iostream>
#include<string>

using namespace std;

int main(){
  string  str;
  
  cin >> str;

  bool sw=true; 
  std::for_each(str.begin(), str.end(), [&](char ch){
      if( sw ){ cout <<  ch << endl; sw=false; }
      else    {                      sw=true;  }
    } );

  return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:12:8: error: 'for_each' is not a member of 'std'
   12 |   std::for_each(str.begin(), str.end(), [&](char ch){
      |        ^~~~~~~~
Language: C++

#include <iostream>
using namespace std;

int main()
{
string s;
cin >> s;

for(int i = 1; i <= s.size(); ++i)
{
if(!(i % == 0))
{
cout << s[i];
}
}
cout << endl;
return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:11:10: error: expected primary-expression before '==' token
   11 | if(!(i % == 0))
      |          ^~
Language: C++

#include<iostream>
#include<string>

using namespace std;

int main(){
  string s;
  cin >> s;
  for(int i=0;i<s.size();0++){
    cout << s[i];
  }
  cout << endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:9:26: error: lvalue required as increment operand
    9 |   for(int i=0;i<s.size();0++){
      |                          ^
Language: C++

#include <bits/stdc++.h>
using namespace std;
#define FOR(i, n) for(int i = 0; i < (n); i++)
#define MEM(a, x) memset(a, x, sizeof(a))
#define ALL(a) a.begin(), a.end()
#define UNIQUE(a) a.erase(unique(ALL(a)), a.end())
typedef long long ll;

string s;

int main(int argc, char const *argv[]) {
	ios_base::sync_with_stdio(false);
	cin >> s;
	for (int i = 0; i < n; i += 2) cout << s[i];
	cout << endl;
	return 0;
}

Compiler output:
a.cc: In function 'int main(int, const char**)':
a.cc:14:29: error: 'n' was not declared in this scope
   14 |         for (int i = 0; i < n; i += 2) cout << s[i];
      |                             ^
Language: C++

#include <iostream>
#include <iomanip>
#include <vector>
#include <algorithm>
#include <cstring>
#include <map>
#include <queue>
#include <cmath>
#include <complex> // complex<double> a(1.2 , 2.3);// real(): 1.2, imag()2.3
using namespace std;

#define MOD 1000000007
#define ll long long
#define ld long double
#define FOR(i,a,b) for(ll i=(ll)a;i<(ll)b;i++)
#define rep(i,n) FOR(i,0,n)
#define pb push_back
#define mp make_pair
#define all(a) a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
#define rmsame(a) sort(all(a)),a.erase(unique(all(a)), a.end())

int main(){
  cin.tie(0);
  ios::sync_with_stdio(false);

  stirng s;
  cin >> s;
  for(ll i =0;i<s.size();i+=2) cout << s[i];
  cout << endl;
  return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:27:3: error: 'stirng' was not declared in this scope
   27 |   stirng s;
      |   ^~~~~~
a.cc:28:10: error: 's' was not declared in this scope
   28 |   cin >> s;
      |          ^
Language: C++

#include <string>
#include <iostream>

int main(){
    string s;
    cin >> s;
    for(int i=0;i<s.size();i+=2)
        cout << s[i];
    cout << endl;
    return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:5:5: error: 'string' was not declared in this scope
    5 |     string s;
      |     ^~~~~~
a.cc:5:5: note: suggested alternatives:
In file included from /usr/include/c++/14/string:41,
                 from a.cc:1:
/usr/include/c++/14/bits/stringfwd.h:77:33: note:   'std::string'
   77 |   typedef basic_string<char>    string;
      |                                 ^~~~~~
/usr/include/c++/14/string:76:11: note:   'std::pmr::string'
   76 |     using string    = basic_string<char>;
      |           ^~~~~~
a.cc:6:5: error: 'cin' was not declared in this scope; did you mean 'std::cin'?
    6 |     cin >> s;
      |     ^~~
      |     std::cin
In file included from a.cc:2:
/usr/include/c++/14/iostream:62:18: note: 'std::cin' declared here
   62 |   extern istream cin;           ///< Linked to standard input
      |                  ^~~
a.cc:6:12: error: 's' was not declared in this scope
    6 |     cin >> s;
      |            ^
a.cc:8:9: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
    8 |         cout << s[i];
      |         ^~~~
      |         std::cout
/usr/include/c++/14/iostream:63:18: note: 'std::cout' declared here
   63 |   extern ostream cout;          ///< Linked to standard output
      |                  ^~~~
a.cc:9:5: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
    9 |     cout << 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:9:13: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
    9 |     cout << 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)
      |     ^~~~