#include <bits/stdc++.h>
using namespace std;
ifstream f("nrtri.in");
ofstream g("nrtri.out");
int v[805],n,a;
int main(){
f>>n;
for(int i=1;i<=n;++i)f>>v[i];
sort(v+1,v+n+1);
for(int i=1;i<=n;++i)for(int j=i+1;j<=n;++j)
for(int k=j+1;v[k]<=v[i]+v[j] && k<=n;++k)a++;
g<<a;
return 0;
}