Language: C++

//Title:
//Writer:Fire Frog
//price:


#define FF Fire Frog

#include<iostream>
#include<cstdio>
#include<string>
#include<cmath>
#include<cstring>
#include<queue>
#include<algorithm>
#include<sstream>
#include<deque>
#include<iomanip>
#include<cctype>
#include<vector>
#include<utility>
#include<windows.h>
#include<time.h>
#include<set>
#include<map>
#include<stdio.h>
#include<stack>
#include<fstream>
#include<stdlib.h>
#include<string.h>
#include<_mingw.h>
#include<stddef.h>
#include<windef.h>
#include<basetyps.h>
#include<shellapi.h>
#include<istream>
#include<rpc.h>
#include<rpcndr.h>
#include<ole2.h>
#include<unknwn.h>
#include<mmstream.h>
#include<winapifamily.h>
#include<time.h>

#define f(i,a,b) for(int (i)=(a);(i)<=(b);i++)
#define F(i,a,b) for(int (i)=(a);(i)<(b);(i)++)

#define all(x) x.begin(),x.end()
#define pb push_back
#define pf push_front
#define mp make_pair
#define fr front
#define ba back
#define fi first
#define se second
#define puf pop_front
#define pub pop_back
#define _p pop
#define P push
#define ms(TV,bb) memset(TV,bb,sizeof(TV))

#define bfd_get_section_name(bfd, ptr) ((ptr)->name + 0)
#define bfd_get_section_vma(bfd, ptr) ((ptr)->vma + 0)
#define bfd_get_section_lma(bfd, ptr) ((ptr)->lma + 0)
#define bfd_get_section_alignment(bfd, ptr) ((ptr)->alignment_power + 0)
#define bfd_section_name(bfd, ptr) ((ptr)->name)
#define bfd_section_size(bfd, ptr) ((ptr)->size)
#define bfd_get_section_size(ptr) ((ptr)->size)
#define bfd_section_vma(bfd, ptr) ((ptr)->vma)
#define bfd_section_lma(bfd, ptr) ((ptr)->lma)
#define bfd_section_alignment(bfd, ptr) ((ptr)->alignment_power)
#define bfd_get_section_flags(bfd, ptr) ((ptr)->flags + 0)
#define bfd_get_section_userdata(bfd, ptr) ((ptr)->userdata)

#define CIN_FILE "input.txt"
#define COUT_FILE "output.txt"

#define pi 3.1415926535897932384626433832795028841971693993751058
#define INT 2147483647
#define MOD 100005
#define AL 26
#define INF (1<<29)
#define NMAX 400
#define M_E		2.7182818284590452354
#define M_LOG2E		1.4426950408889634074
#define M_LOG10E	0.43429448190325182765
#define M_LN2		0.69314718055994530942
#define M_LN10		2.30258509299404568402
#define M_PI		3.14159265358979323846
#define M_PI_2		1.57079632679489661923
#define M_PI_4		0.78539816339744830962
#define M_1_PI		0.31830988618379067154
#define M_2_PI		0.63661977236758134308
#define M_2_SQRTPI	1.12837916709551257390
#define M_SQRT2		1.41421356237309504880
#define M_SQRT1_2	0.70710678118654752440

#define vi vector<int>
#define vii vector<vector<int> >

#define IOS ios::sync_with_stdio(false)
#define BASE ios_base::sync_with_stdio(0)

#define Exit _CRTIMP void __cdecl __MINGW_NOTHROW exit (int) __MINGW_ATTRIB_NORETURN
#define Freopen _CRTIMP FILE* __cdecl __MINGW_NOTHROW freopen (const char*, const char*, FILE*)
#define Putchar __CRT_INLINE __cdecl int __MINGW_NOTHROW putchar(int __c)
#define Asleep WINBASEAPI void WINAPI Sleep (DWORD)
#define Isdigit _CRTIMP int __cdecl __MINGW_NOTHROW isdigit (int)

typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;

using namespace std;

const ull BIG_M=1e9+7;
const ull SIX_M=6666666666;
const ull EIGHT_M=8888888888;
const ull Cstring=1100100;

inline int Read()
{
    int x=0,f=1,c=getchar();
    for(;!isdigit(c);c=getchar())if(c=='-')f=-1;
    for(;isdigit(c);c=getchar())x=x*10+c-'0';
    return x*f;
}

int main(void)
{
	IOS;BASE;

	/*****************************************
	#ifndef ONLINE_JUDGE
		freopen(CIN_FILE,"r",stdin);
		freopen(COUT_FILE,"w",stdout);
	#endif
	*****************************************/
	
	char c[100][100];
	F(i,0,3)cin>>c[i];
	cout<<c[0][0]<<c[1][1]<<c[2][2];

	return 0;
}

Compiler output:
a.cc:21:9: fatal error: windows.h: No such file or directory
   21 | #include<windows.h>
      |         ^~~~~~~~~~~
compilation terminated.