#include<bits/stdc++.h>
using namespace std;
int main()
{
	char a[255];
	scanf("%s",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
			cout<<"G";
	}
	return 0; 
}