#include <fstream>

using namespace std;

int main()
{
    ifstream in("nrtri.in");
    ofstream out("nrtri.out");
    int v[1001], n, i, j, k, nr=0;

    in >> n;

    for( i=1; i<=n; i++ ) {
        in >> v[i];
    }

    for( i=1; i<=n-1; i++ ) {
       for( j=i+1; j<n; j++ ) {
            for( k=j+1; k<=n; k++ ) {
                if( v[i] + v[j] >= v[k] && v[i] + v[k] >= v[j] && v[j] + v[k] >= v[i]  ) {
                    nr++;
                }
            }
       }
    }

    out << nr;

    return 0;
}