#include <fstream>
#include <algorithm>
using namespace std;

ifstream cin("nrtri.in");
ofstream cout ("nrtri.out");

int n,v[1001],a,b,sol;

int caut(int st, int S){
    int dr = n;
    while (st <=dr){
        int mid = (st+dr)/2;

        if (v[mid] <= S)
        st = mid+1;
        else
        dr = mid-1;
    }
    return dr;
}

int main(){
    cin >> n;
    for (int i = 1; i <=n;++i)
        cin >> v[i];
    sort(1+v, v+n+1);
    for(int i = 1; i <=n-2;++i)
    for (int j = i+1; j <=n-1;++j)
    sol += caut(j+1, v[i]+v[j])-j;
    cout << sol;
}