#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int n;
  cin >> n;
  vector<int> v;
  int temp = 0;
  for (int i = 0; i < n; i++) {
    cin >> temp;
    v.push_back(temp);
  }
  int dem0 = 0;
  if (n == 1) {
    if (v[0] == 1)
      cout << "YES";
    else
      cout << "NO";
  } else {
    for (int i = 0; i < n; i++) {
      if (v[i] == 0) dem0++;
    }
    if (dem0 == 0 || dem0 > 1)
      cout << "NO";
    else
      cout << "YES";
  }
  return 0;
}
