题解哦，亲！

#include<bits/stdc++.h>
#include<string>
using namespace std;
string a;
int main(){
	cin>>a;
	for(auto i:a)
	{
		if(i=='T') cout<<"A";
		else if(i=='A') cout<<"T";
		else if(i=='G') cout<<"C";
		else cout<<"G";
	}
}