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

#define DIM 805

using namespace std;

ifstream fi("nrtri.in");
ofstream fo("nrtri.out");

int n;
int A[DIM];
int res;

int main() {
    cin>>n;
    for(int i=1;i<=n;i++) {
        cin>>A[i];
    }
    sort(A+1, A+n+1);

    for(int i=1;i<=n;i++)
        for(int j=i+1;j<=n;j++) {
            res+=(upper_bound(A+1, A+n+1, A[i]+A[j])-A)-1-j;
        }

    cout<<res;
    return 0;
}