#include<bits/stdc++.h>
using namespace std;
ifstream F("nrtri.in");
ofstream G("nrtri.out");
int n,a[800],i,j,t,l,k;
int main()
{
    for(F>>n;j<n;F>>a[j++]);
    for(sort(a,a+n);i<n-2;++i)
        for(j=i+1,t=j+1;j<n-1;k=upper_bound(a+t,a+n,a[i]+a[j])-a,t=k,l+=k-j-1,++j);
    return G<<l,0;
}