题解

#include<iostream>
#include<cstring>
using namespace std;
int main(){
	char a[256];
    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;
}