#include <algorithm>
#include <fstream>

using namespace std;

ifstream fin("nrtri.in");
ofstream fout("nrtri.out");

const int nmax= 800;

int v[nmax+1];

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

    sort( v+1, v+n+1 );

    int n2;
    for ( n2= 1; n2<=n; n2<<= 1 ) {
    }

    int sol= 0;
    for ( int i= 1; i<=n-2; ++i ) {
        for ( int j= i+1; j<=n-1; ++j ) {
            int k= 1;
            for ( int step= n2; step>0; step>>= 1 ) {
                if ( k+step<=n && v[i]+v[j]>=v[k+step] ) {
                    k+= step;
                }
            }

            sol+= k-j;
        }
    }

    fout<<sol<<"\n";

    return 0;
}