#include <bits/stdc++.h>

using namespace std;

namespace {

    typedef double real;
    typedef long long ll;

    template<class T> ostream& operator<<(ostream& os, const vector<T>& vs) {
        if (vs.empty()) return os << "[]";
        os << "[" << vs[0];
        for (int i = 1; i < vs.size(); i++) os << " " << vs[i];
        return os << "]";
    }
    template<class T> istream& operator>>(istream& is, vector<T>& vs) {
        for (auto it = vs.begin(); it != vs.end(); it++) is >> *it;
        return is;
    }

    int N;
    string S;
    void input() {
        cin >> N >> S;
    }

    bool C() {
        for (int i = 0; i < N - 1; i++) {
            if (S[i] == S[i + 1]) return true;
        }
        return N >= 4;
    }

    void solve() {
        cout << (C() ? "YES" : "NO") << endl;
    }
}

int main() {
    input(); solve();
    return 0;
}