ac

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