#include <fstream>
#include <vector>
#include <algorithm>

using namespace std;

vector<int> match;

int findFirst(int index, int value) {
    while (match[--index] >= value);

    return index + 1;
}

int binarySearch(int left, int right, int value) {
    int mid;

    while (left <= right) {
        mid = left + ((right - left) >> 1);
        if (match[mid] >= value) {
            mid = findFirst(mid, value);
            return right - mid + 1;
        }
        else left = mid + 1;
    }

    return 0;
}

int main() {
    int noOfMatches;

    ifstream in("nrtri.in");
    in >> noOfMatches;

    for (int i = 0; i < noOfMatches; ++i) {
        int lenOfMatch;
        in >> lenOfMatch;
        match.push_back(lenOfMatch);
    }
    in.close();

    sort(match.begin(), match.end());
    int nrSol = 0;
    for (int i = 1; i < noOfMatches; ++i) {
        nrSol += binarySearch(i, noOfMatches - 1, match[i] + match[i - 1]);
    }

    ofstream out("nrtri.out");
    out << nrSol << '\n';
    out.close();

    return 0;
}