#include <iostream>
#include <algorithm>
#include <cstdlib>
#include <ctime>
#include <vector>
#include <set>
#include <string>
#include <map>
#include <queue>
#include <stack>
#include <cstring>
#include <cstdio>
#include <cmath>
#include <deque>
#define clr(a,b) memset(a,b,sizeof(a))
#define ll long long

using namespace std;

const int maxn=2*1e5+10;
int n,a,f;

int main()
{
	cin>>n;
	while(n--)
	{
		cin>>a;
		if(a==1)f=1;
	}
	if(f)printf("YES\n");
	else printf("NO\n");
}