#include<bits/stdc++.h>
#include"testlib.h"
using ll = long long;
using namespace std;

int main(int argc, char* argv[]){
    const int MIN_N = 1;
    const int MAX_N = 100000;

    registerValidation(argc, argv);
    int n = inf.readInt(MIN_N, MAX_N);
    inf.readEoln();
    string s = inf.readString("[A-C]{" + to_string(n) + "," + to_string(n) + "}");
    inf.readEof();
    return 0;
}