#include <fstream>
#include <algorithm>
using namespace std;
ifstream fin("nrtri.in");
ofstream fout("nrtri.out");
int n, i, j, dr, st, mid, sol, v[1000];
int main(){
    fin >> n;
    for ( i = 1; i <= n; i++ )
        fin >> v[i];
    sort( v + 1, v + n + 1 );
    for ( i = 1; i <= n; i++ ){
        for ( j = i + 1; j <= n; j++ ){
            st = j + 1;
            dr = n;
            while ( st <= dr ){
                mid = ( st + dr ) / 2;
                if (  v[mid]  <= v[i] + v[j] )
                    st = mid + 1;
                else
                    dr = mid - 1;
            }
            sol += dr - j;
        }
    }
    fout << sol;
    return 0;
}