# include <cstdio>
# include <algorithm>

using namespace std;

int i, j, k, n, ct, a[805];
int main()
{
    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);
    
    scanf("%d",&n);
    for (i = 1; i <= n; i++)
    scanf("%d",&a[i]);
    
    sort(a + 1, a + n + 1);
 
    for (i = 1; i <= n; i++)
        for (j = i + 1; j <= n; j++)
            for (k = j + 1; k <= n; k++)
            if ((a[i] > 0 && a[j] > 0 && a[k] > 0) && 
            (a[i] + a[j] >= a[k]) && (a[i] + a[k] >= a[j]) &&
            (a[j] + a[k] >= a[i])) ct++;
                              else break;
            
    printf("%d",ct);

return 0;
}