• 记录字符的个数即可

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N = 1e6 + 10, INF = 0x3f3f3f3f, MOD = 1E9 + 7;

void solve() {
    int n;
    string s;
    cin >> n >> s;
    int mp[2] = {0};
    for (int i = 0; i < n; i++) {
        mp[s[i] - 'A']++;
    }
    cout << (mp[0] > mp[1] ? 'A' : 'B') << endl;
}

int main(int argc, char* argv[]) {
    int t = 1;
    // cin >> t;
    while (t--) {
        solve();
    }
    return 0;
}