#import<bits/stdc++.h>
using namespace std;long v[900],i,j,k,n,r;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;}