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

using ll = long long;

// 制約に書かれている定数を宣言
const ll Nmin = 1, Nmax = 200000;

int main(){
    registerValidation();
    ll N = inf.readLong(Nmin,Nmax);
    inf.readEoln();
    string S = inf.readString();
    assert((ll)(S.size()) == N);
    for(auto c : S){
        assert('A' <= c && c <= 'B');
    }
    inf.readEof();
    return 0;
}