#include <iostream>
#include <algorithm>
#include <cstdio>
using namespace std;

int s, n, a[1000];

int rez(int lg, int x, int incep)
{
    int i;
    for(i = incep; lg; lg>>=1)
        if(i+lg<=n && a[i+lg] <= x)
            i+=lg;
    if(a[i] > x)
        return incep;
    else
        return i;
}

int main()
{
    int lg;
    freopen("nrtri.in", "r", stdin);
    freopen("nrtri.out", "w", stdout);
    scanf("%d\n", &n);
    for(int i = 1; i<=n; ++i)
        scanf("%d ", &a[i]);
    sort(a+1, a+n+1);

    for(int i = 1; i<n-1; ++i)
    {
        for(int j = i+1; j<n; ++j)
        {
            for(lg = 1; lg<n-j; lg<<=1)
            {}
            s+=(rez(lg, a[i]+a[j], j) - j);
        }
    }
    printf("%d", s);
    return 0;
}