# 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;
}