#include <iostream>
#include <string>

void solve() {
    int n;
    std::string s;
    std::cin >> n >> s;

    bool out = true;
    for (int i = 0; i + 1 < n; ++i) {
        if (s[i] == s[i + 1]) out = false;
    }

    std::cout << (n < 4 && out ? "NO" : "YES") << std::endl;
}

int main() {
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);

    solve();

    return 0;
}