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

using namespace std;

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

int v[1005];

int nrtri(int v[],int n){
    int s=0;
    for(int i=1;i<=n-2;++i){
        for(int j=i+1;j<=n-1;j++){
            for(int k=j+1;k<=n;++k){
                if(v[i]+v[j]>=v[k])
                    s++;
                else
                    break;
            }
        }
    }
    return s;
}

int main()
{
    int n;
    f >>n;
    for(int i=1;i<=n;++i)
        f >>v[i];
    sort(v+1,v+n+1);
    g <<nrtri(v,n);
    return 0;
}