# include <bits/stdc++.h>

using namespace std;
string s,s1;
int main(){
	cin>>s;
	for(int i = 0;i<s.size();i++){
		switch(s[i]){
			case 'A':s1+='T';break;
			case 'T':s1+='A';break;
			case 'G':s1+='C';break;
			case 'C':s1+='G';break;
		}
	}
	cout<<s1;
	return 0;
}

#include<iomanip> 
#include<cmath> 
#include<cstdio> 
#include<cstring> 
#include<algorithm> 
const int N=1e7+8;
const int INF=0x3f3f3f3f;
using namespace std;
int n,m;
char a[N],b[N];
int main()
{
	cin>>a;
	int len=strlen(a);
	for(int i=0;i<len;i++)
	{
		if(a[i]=='A')
		{
			b[i]='T';
		}
		else if(a[i]=='T')
		{
			b[i]='A';
		}
		else if(a[i]=='G')
		{
			b[i]='C';
		}
		else if(a[i]=='C')
		{
			b[i]='G';
		}
	}
	cout<<b;
	return 0;
}

#include<bits/stdc++.h>
using namespace std;
char ch;
char findd(char x)
{
	if(x=='A')return 'T';
	if(x=='T')return 'A';
	if(x=='G')return 'C';
	return 'G';
}
int main()
{
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	while(cin>>ch)
	{
		cout<<findd(ch);
	}
	return 0;
}

#include <bits/stdc++.h>
char turn(char x){
	if(x == 'A'){return 'T';}
	else if(x == 'T'){return 'A';}
	else if(x == 'G'){return 'C';}
	else{return 'G';}
}
char a[114514];
using namespace std;
const int N = 1e5 + 10;
const int INF = 0x3f3f3f3f;
int main(){
	cin >> a;
	for(int i = 0;i < strlen(a);i++)
		cout << turn(a[i]);
	}
	return 0;
	}