#include <stdio.h>
int a[805];
int n,nrt;
int main ()
{
    freopen ("nrtri.in","r",stdin);
    freopen ("nrtri.out","w",stdout);
    int i,j,k;
    scanf ("%d",&n);
    for (i=1; i<=n; ++i)
        scanf ("%d",&a[i]);
    for (i=1; i<=n-2; ++i)
        for (j=i+1; j<=n-1; ++j)
            for (k=j+1; k<=n; ++k)
                if ((a[i]+a[j]>=a[k]) && (a[i]+a[k]>=a[j]) && (a[k]+a[j]>=a[i]))
                    ++nrt;
    printf ("%d",nrt);
    return 0;
}