#include <bits/stdc++.h>
using namespace std;
ifstream in  ("nrtri.in");
ofstream out ("nrtri.out");
int v[801],n;
int main()
{
    int contor=0,i,j,m;
     in>>n;
    for(i=1;i<=n;i++)
        in>>v[i];
    sort(v+1,v+n+1);
    for(i=1;i<=n-2;i++)
        for(j=i+1;j<=n-1;j++)
        for(m=j+1;m<=n;m++)
    {
    if(v[m]<=v[i]+v[j])
        contor++;
    else
        break;
    }
    out<<contor;
    return 0;
}