#include<bits/stdc++.h>
using namespace std;
#define ll long long
const int maxn = 1e5 + 5;
const int inf=0x3f3f3f3f;

int main()
{
	int n;
	cin>>n;
	for(int i=1;i<+n;i++)
	{
		int a;
		cin>>a;
		if(a==1)
		{
			cout<<"YES"<<endl;
			return 0;
		}
	}
	cout<<"NO"<<endl;
}