文件目录

#include <iostream>
using namespace std;
int main()
{
    string s;
    cin >> s;
    for (int i = 0; s[i]; i++)
        if (s[i] == 'A')
            cout << "T";
        else if (s[i] == 'T')
            cout << "A";
        else if (s[i] == 'C')
            cout << "G";
        else
            cout << "C";
    return 0;
}