#include<iostream>
using namespace std;
int main()
{
	string a;
	cin>>a;
    int	length=a.size();
    string b;
    for(int i=0;i<=length-1;i++)
        {
			if(a[i]=='A')
			   {
			   	b[i]='T';
			   }
			if(a[i]=='T')
				{
			 	b[i]='A';
				}
			if(a[i]=='C')
				{
				b[i]='G';
				}
			if(a[i]=='G')
				{
				b[i]='C';
				}
			cout<<b[i]; 
		}
	
	
	return 0;
}