Time Limit: 3 s

Description

Given n numbers, your task is to insert '+' or '-' in front of each number to construct expressions. Note that the position of numbers can be also changed. You can calculate a result for each expression. Please count the number of distinct results and output it.

Input

There are several cases. For each test case, the first line contains an integer n (1 ≤ n ≤ 20), and the second line contains n integers a₁,a₂, ... ,a_n(-1,000,000,000 ≤ a_i ≤ 1,000,000,000).

Output

For each test case, output one line with the number of distinct results

Sample Input

2
1 2
3
1 3 5

 Sample Output

48 本題題意： 這題說的是第一行給你一個n,接下來一行給你n個數，可以在這n 個數前邊加“+”或者“-”，計算這些數的和，輸出有幾種不同的和。 解題思路： 因為資料比較小，直接暴力深搜就可以。 程式碼：

#include <iostream>
#include <algorithm>
#include <map>
#include <cstdio>
using namespace std;
int a[25];
map <int,int> M;
int n,ans;
void dfs(int sum,int i)
{
    if(i==n+1)
    {
        if(M[sum]==0)///如果沒有出現過
        {
            M[sum]=1;
            ans++;
        }
        return;
    }
    dfs(sum+a[i],i+1);
    dfs(sum-a[i],i+1);
}
int main()
{
    while(~scanf("%d",&n))
    {
        for(int i=0; i<n; i++)
            scanf("%d",&a[i]);
        M.clear();
        ans=0;
        dfs(0,0);
        printf("%d\n",ans);
    }
    return 0;
}
 

Output