#include <bits/stdc++.h>

using namespace std;

ifstream f("nrtri.in");
ofstream g("nrtri.out");


int n,v[805],su[805],cont,dif,s,ante;

int main()
{
    f >> n;
    for(int i = 1;i<=n;i++)
    {
        f >> v[i];
       // su[i] = su[i-1] + v[i];
    }
    /*sort(su+1,su+1+n);
    sort(v+1,v+1+n);

    for(int i = n;i>=n;i--)
    {
        if(s[i] - s[i-1] >=0)
        {
            dif = (s[i] - s[i-1]);
            if(v[i] - dif > 0)
            {
                cont = cont + 1 +
            }
        }
    }*/
    sort(v+1,v+1+n);
    for(int i = 1;i<=n-2;i++)
    {
        for(int j = i+1;j<=n-1;j++)
        {
            for(int d = j+1;d<=n;d++)
            {
                if(v[i]+v[j] >= v[d])
                {
                    cont++;
                }
                if(v[d] > v[i] + v[j])
                {
                    break;
                }
            }
        }
    }
    g << cont;
    return 0;
}