A. Fashion in Berland

题目连接：

http://www.codeforces.com/contest/691/problem/A

Description

According to rules of the Berland fashion, a jacket should be fastened by all the buttons except only one, but not necessarily it should be the last one. Also if the jacket has only one button, it should be fastened, so the jacket will not swinging open.

You are given a jacket with n buttons. Determine if it is fastened in a right way.

Input

The first line contains integer n (1 ≤ n ≤ 1000) — the number of buttons on the jacket.

The second line contains n integers ai (0 ≤ ai ≤ 1). The number ai = 0 if the i-th button is not fastened. Otherwise ai = 1.

Output

In the only line print the word “YES” if the jacket is fastened in a right way. Otherwise print the word “NO”.

Sample Input

3
1 0 1

Sample Output

YES

Hint

题意

给你n个数，如果数只有1个的话，那就这个数必须是1，否则的话，就必须只有一个0

题解：

水题

代码

#include<bits/stdc++.h>
using namespace std;
const int maxn = 1005;
int main(){
    int n;
    scanf("%d",&n);
    int num1 = 0,num2 = 0;
    for(int i=1;i<=n;i++){
        int x;
        scanf("%d",&x);
        if(x==1)num1++;
        else num2++;
    }
    if(num1+num2==1&&num1==1){
        return puts("YES");
    }else if(num1+num2>1&&num2==1){
        return puts("YES");
    }
    puts("NO");
}