#include <stdio.h>
int i,j,k,a[805],n;
long p=0;
int main()
{
    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);
    scanf("%ld\n",&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[k]+a[j]>=a[i]&&
       a[i]+a[k]>=a[j])
    p++;
    printf("%ld",p);
    return 0;
}