#include <iostream>
#include <fstream>
#include <algorithm>
using namespace std;
ifstream in("nrtri.in");
ofstream out("nrtri.out");
int n,v[1000],i,j,a,contor,k;
int main()
{
in>>n;
for(i=1;i<=n;i++)
    in>>v[i];
sort(v+1,v+n+1);
for(i=1;i<n;i++)
    for(j=i+1;j<=n;j++)
    {
        a=v[i]+v[j];
        for(k=j+1;k<=n;k++)
                if(a>=v[k])
                contor++;
    }
    out<<contor;
    return 0;
}