#include<iostream>
using namespace std;
int x[101], y, z[10001], i, j, m, n;
int main()
{
    cin >> y;
    for (i = 0; i < y; i++)
    {
        cin >> x[i];
    }
    for (i = 0; i < y; i++)
    {
        for (j = i+1; j < y; j++)
        {
            if (x[i] != x[j])
            {
                z[m] = x[i] + x[j];
                m++;
            }
        }
    }
    for (i = 0; i < y; i++)
    {
        for (j = 0, m = 0; j < y*y; j++)
        {
            if (x[i] == z[j])
            {
                z[j] = -1;
                m++;
            }
            if (m != 0)
            {
                z[i] = -1;
            }
        }
        if (z[i] == -1 && m != 0)n++;
    }
    cout << n;
}