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

int v[800],n,i,j,k,s;


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

    f>>n;
    for (i=1;i<=n;i++)
        f>>v[i];

    sort(v+1,v+n+1);

    for (i=1;i<=n;i++)
        for (j=i+1;j<=n-1;j++)
            for(k=j+1;k<=n;k++)
                if (v[i]+v[j]>=v[k]) s++;
                    else break;
    g<<s;

    return 0;
}