#include <iostream>
#include <fstream>

using namespace std;
ifstream f("nrtri.in");
ofstream g("nrtri.out");
int bule(int (&v)[1000], int n)
{
    int ok,i,aux;
    do
    {
        ok=1;
        for(i=1; i<=n-1; i++)
            if(v[i]>v[i+1])
            {
                ok=0;
                aux=v[i];
                v[i]=v[i+1];
                v[i+1]=aux;
            }
    }
    while(ok!=1);
}
int main()
{
    int N,v[1000],i,t=0,k,j,x,rez=0;
    f>>N;
    for (i=1; i<=N; i++)
        f>>v[i];
    bule (v,N);
    for (i=1; i<=N-2; i++)
    {
        k=i+2;
        for (j=i+1; j<=N-1; j++)
        {
            x=v[i]+v[j];
            while (x>=v[k]&&k<=N)
                k++;
            if (k>j-1)
                rez+=k-j-1;
        }
    }
    g << rez << endl;
    return 0;
}