#include <iostream>
#include <fstream>
#include <cmath>
#include <algorithm>

using namespace std;

ifstream fin("nrtri.in");
ofstream fout("nrtri.out");

int v[805];

int gas(int lf,int rg,int cautat){
    int x=lf-1;
    while(lf<=rg){
        int mid=(lf+rg)/2;
        if(v[mid]<=cautat){
            lf=mid+1;
            x=mid;
        }
        else
            rg=mid-1;
    }
    return x;
}

int main(){
    int n;
    fin >> n;
    for(int i=0;i<n;i++)
        fin >> v[i];
    sort(v,v+n);
    int rasp=0;
    for(int i=0;i<n;i++)
        for(int j=i+1;j<n;j++) {
            int pos_gasit=gas(j+1,n-1,v[i]+v[j]);
            rasp+=pos_gasit-j;
        }
    fout << rasp;
}