#include <bits/stdc++.h>
using namespace std;
int main()
{
	int n,j,pos = 1,cnt = 0;
	cin >> n;
	for(int i = 1;i <= n;i ++)
	{
		cin >> j;
		if(pos == i)
		{
			if(pos == n)
			{
				cout << "YES" << endl << cnt << endl;
				break;
			}
			pos += j;
			cnt ++;
		}
	}
	if(pos > n)
		cout << "NO" << endl << cnt << endl;
	return 0;
}