#include <iostream>
#include <algorithm>
using namespace std;

int main(){
    int H[3], W[3];
    string alphabets[3] = {"A", "B", "C"};
    for(int i = 0; i < 3; i++){
        cin >> H[3] >> W[3];
    }
    int H_tmp[3];
    int W_tmp[3];
    for(int i = 0; i < 3; i++){
        H_tmp[i] = H[i];
        W_tmp[i] = W[i];
    }
    sort(H_tmp, H_tmp + 3);
    sort(W_tmp, W_tmp + 3);
    if(H_tmp[0] == H_tmp[1] && H_tmp[1] == H_tmp[2]){
        for(int i = 0; i < 3; i++){
            for(int j = 0; j < 3; j++){
                if(W_tmp[i] == W[j]){
                    cout << alphabets[j] << endl;
                    break;
                }
            }
        }
    }else if(H_tmp[0] == H_tmp[1]){
        for(int i = 0; i < 2; i++){
            for(int j = 0; j < 3; j++){
                if(W_tmp[i] == W[j]){
                    cout << alphabets[j] << endl;
                    break;
                }
            }
        }
        for(int i = 0; i < 3; i++){
            if(W_tmp[2] == W[i]){
                cout << alphabets[i] << endl;
                break;
            }
        }
    }else if(H_tmp[0] == H_tmp[1]){
        for(int i = 0; i < 3; i++){
            if(W_tmp[0] == W[i]){
                cout << alphabets[i] << endl;
                break;
            }
        }
        for(int i = 1; i < 3; i++){
            for(int j = 0; j < 3; j++){
                if(W_tmp[i] == W[j]){
                    cout << alphabets[j] << endl;
                    break;
                }
            }
        }
    }else{
        for(int i = 0; i < 3; i++){
            for(int j = 0; j < 3; j++){
                if(H_tmp[i] == H[j]){
                    cout << alphabets[j] << endl;
                    break;
                }
            }
        }
    }
}