#include <stdio.h>
#define abs(a) ((a<0)?-a:a)

int main(){
    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);
    
    long n,i,j,k,q=0,a[1024],x;
    
    scanf("%ld",&n);
    for (i=1;i<=n;i++)
        scanf("%ld",&a[i]);
    for (i=1;i<n-1;i++)
        for (j=i+1;j<n;j++)
            for (k=j+1;k<=n;k++)
                if (a[i]+a[j]>=a[k])
                   if (abs((a[i]-a[j]))<=a[k])
                      q++;
    printf("%ld\n",q);
    
return 0;
}