#include<bits/stdc++.h>
using namespace std;
int main(){
	string a;cin>>a;
	for(int i=0;i<a.size();i++){
		if(a[i]=='A') cout<<"T";
		if(a[i]=='C') cout<<"G";
		if(a[i]=='T') cout<<"A";
		if(a[i]=='G') cout<<"C";
    }
	return 0;
}