#include <iostream>
using namespace std;

const int MAXN = 105;
int nums[MAXN];
bool isSum[MAXN];

int main() {
    int n;
    cin >> n;

    // 读取正整数集合
    for (int i = 0; i < n; i++) {
        cin >> nums[i];
    }

    // 遍历所有可能的两数之和
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            if (i == j) continue;
            for (int k = 0; k < n; k++) {
                if (nums[k] == nums[i] + nums[j]) {
                    isSum[k] = true;
                }
            }
        }
    }

    int count = 0;
    // 统计满足条件的数的个数
    for (int i = 0; i < n; i++) {
        if (isSum[i]) {
            count++;
        }
    }

    cout << count << endl;

    return 0;
}    
/**************************************************************
	Problem: 1594
	User: linmiaoling
	Language: C++
	Result: Accepted
	Time:40 ms
	Memory:2072 kb
****************************************************************/