#include <stdio.h>
int i,j,k,a[805],n,x,mid;
long p=0;

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