#include <bits/stdc++.h>
using namespace std;
#define rep(i,a,b) for(int i=a;i<b;i++)

int main()
{
	int N; cin >> N;
	string S; cin >> S;

	string ans = "YES";
	if (S == "0") ans = "NO";
	if (S == "1") ans = "NO";
	if (S == "01") ans = "NO";
	if (S == "10") ans = "NO";
	if (S == "010") ans = "NO";
	if (S == "101") ans = "NO";
	cout << ans << endl;
}