#include <fstream>
using namespace std;

int N, V[805], S[60005], rasp;

int main()
{
    fstream fin("nrtri.in",ios::in);
    fstream fout("nrtri.out",ios::out);

    fin >> N;
    for(int i = 1; i <= N; ++ i)
    {
        fin >> V[i];
        for(int j = 1; j < i; ++ j)
            S[V[i] + V[j]] ++;
    }

    for(int i = 1; i < 6005; ++ i)
        S[i] += S[i - 1];

    rasp = (N * (N - 1) * (N - 2)) / 6;
    for(int i = 1; i <= N; ++ i)
        rasp -= S[ V[i] - 1 ];

    fout << rasp;

    return 0;
}