#include <bits/stdc++.h>
using namespace std;

int a[1000];
int main(void){
    ofstream cout("nrtri.out");
    ifstream cin("nrtri.in");
    int n;
    cin >> n;
    for(int i=1;i<=n;i++){
        cin >> a[i];
    }
    int cnt= 0;
    sort(a+1, a+n+1);
    for(int i = 1;i<=n-2;i++){
        for(int j = i+1;j<=n-1;j++){
            //facem cautarea binara
            int st = j+1;
            int dr = n;
            int mij = 0;
            while(st <= dr){
                mij = (st+dr)/2;
                if(a[i] + a[j] >= a[mij]){
                    st = mij+1;
                }else{
                    dr = mij-1;
                }
            }
            cnt += (dr - j);
        }
    }
    cout << cnt;
}