//Numarare triunghiuri
#include <bits/stdc++.h>
using namespace std;

ifstream fin ("nrtri.in");
ofstream fout ("nrtri.out");

int main()
{
    int nr,n[802],r=0;
    fin>>nr;
    for(int i=1;i<=nr;i++)
    {
        fin>>n[i];
    }
    sort(n+1,n+nr+1);
    for(int i=1;i<=nr;i++)
    {
        int j=i+1;
        for(int k=j+1;k<=nr;k++)
        {
            if(n[i]+n[j]>=n[k])
            {
                r++;
                //fout<<n[i]<<" "<<n[j]<<" "<<n[k]<<"\n";
            }
        }
    }
    fout<<r;
	return 0;
}