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

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


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-2,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;
}