#include <bits/stdc++.h>
using namespace std;

int main() {
    map<int, char> m;
    for (int i = 0; i < 3; i++) {
        int h;
        cin >> h;
        m[h] = 'A' + i;
    }
    for (auto x : m) {
        cout << x.second << endl;
    }
}