#include <iostream>
#include <algorithm>
#include <fstream>
using namespace std;
ifstream in("nrtri.in");
ofstream out("nrtri.out");
int main(){
    int n, v[801], i, j, k, nr = 0;
    in>>n;
    for(i = 1; i <= n; i++)
        in>>v[i];
    sort(v + 1, v + n + 1);
    for(i = 1; i <= n - 2; i++){
        for(j = i + 1; j <= n - 1; j++){
            for(k = j + 1; k <= n; k++){
                if(v[i] + v[j] >= v[k])
                    nr++;
                else
                    break;
            }
        }
    }
    out<<nr;
}