#include <iostream>
#include <iomanip>
#include <vector>
#include <algorithm>
#include <numeric>
#include <functional>
#include <cmath>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <sstream>
#include <string>

#define repd(i,a,b) for (int i=(a);i<(b);i++)
#define rep(i,n) repd(i,0,n)
#define var auto
#define mod 1000000007
#define inf 2147483647
typedef long long ll;

using namespace std;

int inputValue(){
    int a;
    cin >> a;
    return a;
}

template <typename T>
void output(T a, int precision) {
    if(precision > 0){
        cout << fixed << setprecision(precision)  << a << "\n";
    }
    else{
        cout << a << "\n";
    }
}

// end of template

int main() {
    // source code
    
    int N = inputValue();
    string s;
    cin >> s;
    
    if (N == 1) {
        output("NO", 0);
        return 0;
    }
    else if(s == "01" || s == "10" || s == "101" || s == "010"){
        output("NO", 0);
        return 0;
    }
    output("YES", 0);
    
    return 0;
}