//
#include <bits/stdc++.h>
using namespace std;
char a[1000];
int main()
{
	cin>>a;
	for (int i=0;i<strlen(a);i++)
	{
		if (a[i]=='A')
			cout<<"T";
		else if (a[i]=='T')
			cout<<"A";
		else if (a[i]=='G')
			cout<<"c";
		else if (a[i]=='C')
			cout<<"G";
	}
	return 0;
}