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

const int NMAX = 8e2+1;
int N, vec[NMAX], nr;

void citire()
{
    freopen("nrtri.in", "r", stdin);
    freopen("nrtri.out", "w", stdout);

    scanf("%d", &N);
    for(int i = 1; i <= N; i++) scanf("%d", &vec[i]);
}
/*
void cautare(int i, j)
{
    int left = j, right = N;
    while(left < )
}
*/
int main()
{
    citire();
    int k;
    sort(vec+1, vec+N+1);
    for(int i = 1; i <= N; i++)
    {
        k = i + 2;
        for(int j = i+1; j <= N; j++)
        {
            while(k <= N && vec[i]+vec[j] >= vec[k])
                k++;
            if(k-j-1 > 0)
                nr = nr + k - j - 1;
        }
    }
    printf("%d", nr);
    return 0;
}