#include<bits/stdc++.h>
#define in f
#define out g
using namespace std;

ifstream f ("nrtri.in");
ofstream g ("nrtri.out");

int n;
int v[801];
int r;

int main() {
    
    in >> n;
    for(int i = 1; i <= n; i++) {
        in >> v[i];
    }
    sort (v + 1, v + n + 1);
    for(int i = 1; i < n; i++) {
        for(int j = i + 2; j <= n; j++) {
            for(int k = j - 1; k > i; k--) {
                if((v[i] + v[j] >= v[k]) && (v[i] + v[k] >= v[j]) && (v[j] + v[k] >= v[i])){
                    r++;
                } else
                    break;
            }
        }
    }
    out << r;
    return 0;
}