#include <bits/stdc++.h>
using namespace std ;
int main ( )
{
    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);
    int n , v [ 805 ] , nrtri = 0 ; cin >> n ;
    for ( int i = 0 ; i < n ; i ++ )
    {
        cin >> v [ i ] ;
    }
    sort ( v , v + n ) ;
    for ( int i = 0 ; i < n ; i ++ )
        for ( int j = i + 1 ; j < n ; j ++ )
            for ( int p = j + 1 ; p < n ; p ++ )
            {
                if ( v [ p ] > ( v [ i ] + v [ j ] ) )
                    break ;
                nrtri ++ ;
            }
    cout << nrtri ;
    return 0 ;
}