#include <cstdio>
#include <cstring>
#include <iostream>
#include <string>
#include <cmath>
#include <bitset>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <deque>
#include <algorithm>
#include <complex>
#include <unordered_map>
#include <unordered_set>
#include <random>
#include <cassert>
#include <fstream>
#define popcount __builtin_popcount
using namespace std;
typedef long long int ll;
typedef pair<ll, ll> P;

int main()
{
    int n; cin>>n;
    string s; cin>>s;
    if(n==1 || s=="01" || s=="10" || s=="101" || s=="010") cout<<"NO"<<endl;
    else cout<<"YES"<<endl;
    return 0;
}