#include <bits/stdc++.h>
using namespace std;
#define REP(i, n) for(int i=0 ; (i)<(int)(n) ; (i)++)

int main(void){
    int n;
    cin >> n;
    bool ichi = false, zero = false;
    REP(i, n){
        int a;
        cin >> a;
        if(a == 1) ichi = true;
        if(a == 0) zero = true;
    }
    if(ichi == true || zero == true) cout << "Yes" << endl;
    else cout << "No" << endl;
}