#include <fstream>
#include <algorithm>
using namespace std;
ifstream cin("nrtri.in");
ofstream cout("nrtri.out");
int N,v[805];
int main()
{
    cin>>N;
    for(int i=1;i<=N;i++){
        cin>>v[i];
    }
    sort(v+1,v+N+1);
    int solutie=0;
    for(int i=1;i<=N;i++){
        for(int j=i+1;j<=N;j++){
            int st = j, dr = N, rasp;
            while(st <= dr){
                int mij = (st+dr)/2;
                if(v[mij] <= v[i] + v[j]){
                    st = mij + 1;
                    rasp = mij;
                }
                else{
                    dr = mij - 1;
                }
            }
            solutie = solutie + rasp - j;
        }
    }
    cout<<solutie;
}