#include <bits/stdc++.h>
using namespace std;

int main() {
    int64_t n, x;
    cin >> n >>  x;
    vector<int64_t> as(n);
    for (auto &a : as) {
        cin >> a;
    }
    sort(as.begin(), as.end());
    int64_t ans = 0;
    for (int i = 0; i < n; i++) {
        ans += distance(lower_bound(as.begin() + i + 1, as.end(), n - as[i]), upper_bound(as.begin(), as.end(), n - as[i]));
    }
    cout << ans << endl;
    return 0;
}