CF #248 A. Kitahara Haruki's Gift

time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standard output

Kitahara Haruki has bought n apples for Touma Kazusa and Ogiso Setsuna. Now he wants to divide all the apples between the friends.

Each apple weights 100 grams or 200 grams. Of course Kitahara Haruki doesn't want to offend any of his friend. Therefore the total weight of the apples given to Touma Kazusa must be equal to the total weight of the apples given to Ogiso Setsuna.

But unfortunately Kitahara Haruki doesn't have a knife right now, so he cannot split any apple into some parts. Please, tell him: is it possible to divide all the apples in a fair way between his friends?
Input

The first line contains an integer n (1 ≤ n ≤ 100) — the number of apples. The second line contains n integers w1, w2, ..., wn (wi = 100 or wi = 200), where wi is the weight of the i-th apple.
Output

In a single line print "YES" (without the quotes) if it is possible to divide all the apples between his friends. Otherwise print "NO" (without the quotes).
Sample test(s)
Input

3
100 200 100

Output

YES

Input

4
100 100 100 200

Output

NO

Note

In the first test sample Kitahara Haruki can give the first and the last apple to Ogiso Setsuna and the middle apple to Touma Kazusa.

今天下午睡了一觉，起来都4点半了。。赶紧打开CF。。水题，由于只有两种重量，dp都用不着了，比武大那个热身赛的dp题目还水，直接暴力解一个一元二次不定方程就过了，代码如下

#include <cstdio>
#include <iostream>
#include <cstring>
using namespace std;

int main(){
    int n;
    while(~scanf("%d", &n)){
        int s1 = 0, s2 = 0, num;
        for(int i=1; i<=n; i++){
            scanf("%d", &num);
            if(num == 100) s1++;
            else s2++;
        }
        int sum = s1 + 2*s2;
        if(sum%2 == 1){
            puts("NO");
            continue;
        }
        else{
            sum /= 2;
            bool flag = 0;
            for(int y = s2; y >= 0; y--){
                int x = sum - 2*y;
                if(x >= 0 && x <= s1){
                    flag = 1;
                    break;
                }
            }
            if(flag == 1) puts("YES");
            else puts("NO");
        }
    }
    return 0;
}