#include <iostream>
#include <cstdio>
#include <vector>
#include <string>

using namespace std;

int main() {
	int n;
	string s;
	cin >> n >> s;

	bool ok = true;
	if (n == 1 || s == "01" || s == "10" || s == "010" || s == "101") {
		ok = false;
	}

	cout << (ok ? "YES" : "NO") << endl;

	return 0;
}