#include <iostream>
#include <fstream>
#include <cstring>
#include <string>
#include <climits>
#include <algorithm>
using namespace std;
ifstream fin ("nrtri.in");
ofstream fout("nrtri.out");

#define MAX 801

int n,a[MAX],i,j,k;



void sort()
{
    int ok,k=0;
    do
    {
        ok=1;
        for(i=1;i<n-k;i++)
        {
            if(a[i]>a[i+1])
            {
                int t=a[i];
                a[i]=a[i+1];
                a[i+1]=t;
                ok=0;
            }
        }
        k++;
    }while(!ok);
}


int main()
{
    fin>>n;
    for(i=1;i<=n;i++)
    {
        fin>>a[i];
    }
    sort(a+1, a+1+n);
    int count=0;
    for(i=1;i<n-1;i++)
    {
        for(j=i+1;j<n;j++)
        {
            for(k=j+1;k<=n;k++)
            {
                if(a[i]+a[j]>=a[k])
                {
                    count++;
                }
                else
                {
                    k=n+1;
                }
            }
        }
    }
    fout<<count;
    return 0;
}