#include <fstream>
#include <algorithm>
using namespace std;

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


int v[1001], ok = 0;


int main()
{
    int n,ok=0,cnt=0
                   in>>n;
    for( int i=1; i<= n; i++)
        in>>v[i];
    sort(v+1,v+n+1 );
    for( int j=1; j<= n; j++)
    {
        for( int i=1; i<j; i++)
        {
            while( cnt <n && v[cnt+1]<=v[a]+v[i])
                ++cnt;
            ok+=max(0,cnt-j);
        }
    }
    out << ok << '\n';
    return 0;
}