#include<bits/stdc++.h>
using namespace std;
ifstream in ("nrtri.in");
ofstream out ("nrtri.out");
int v[801],n;
int main()
{
    int i,j,q,cnt=0;
    in>>n;
    for(i=1; i<=n; i++)
        in>>v[i];
    sort(v+1,v+n+1);
    for(i=1; i<=n-2; i++)
        for(j=i+1; j<=n-1; j++)
            for(q=j+1; q<=n; q++)
              {
               if(v[q]<=v[j]+v[i])
                    cnt++;
               else
                break;
              }

    out<<cnt;
    return 0;
}