#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define all(x) (x).begin(), (x).end()
using ll = long long;
const ll MOD = 998244353;
#include<atcoder/all>
using namespace atcoder;
using mint = modint998244353;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  ll n;cin>>n;
  vector<ll> A(n);
  rep(i,n) cin>>A[i];
  if(*max_element(all(A))==0) {
    cout << "No" << "\n";
  }else{
    cout<<"Yes" << "\n";
  }
}