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

using namespace std;


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

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

int v[805],n,sol=0,st,dr,mij;

int main(){

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

    for(int i=1;i<n;i++){
        for(int j=i+1;j<=n;j++){

            st=j+1;dr=n;
            while(st<=dr){
                mij = (st+dr)/2;
                if(v[mij]>v[i]+v[j]){
                    dr = mij-1;
                }else{
                    st = mij+1;
                }
            }

            sol+=(dr-j);
        }
    }

    g<<sol;

    f.close();
    g.close();
    return 0;
}