#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
using ll = long long;

int main(void){
  int n; cin >> n;
  for(int i=0; i<n; i++){
    int x; cin >> x;
    if(x>0){
      cout << "Yes" << endl; return 0;
    }
  }
  cout << "No" << endl;
  return 0; 
}