#include <fstream>
#include <algorithm>
#include <iostream>
using namespace std;

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

int n,m,i,j,a[805],ap=0,p1,p2,s;

int main()
{
    fin>>n;
    for(i=1;i<=n;i++)
    {
        fin>>a[i];
    }
    sort(a+1,a+n+1);
    for(i=1;i<=n;i++)
    {
        for(j=i+1;j<=n;j++)
        {
            s=a[i]+a[j];
            p2=upper_bound(a+1,a+n+1,s)-a;
            //cout<<p2<<" "<<a[i]<<" "<<a[j]<<endl;
            ap=ap+(p2-j)-1;
        }
    }
    fout<<ap;
    return 0;
}