#include <bits/stdc++.h>
using namespace std;
long v[900],i,j,k,n,r;
int main()
{ifstream f("nrtri.in");
ofstream g("nrtri.out");
f>>n;
for (i=1;i<=n;i++) f>>v[i];
sort(v+1,v+n+1);
for (i=1;i<=n;i++) for (j=i+1;j<=n;j++)
for (k=j+1;k<=n && v[k]<=v[i]+v[j];k++) r++;
g<<r;
return 0;}