#include <stdio.h>

int main()
{

int n,v[800],j,k,i;
long ct=0;

freopen("nrtri.in","r",stdin);
freopen("nrtri.out","w",stdout);

scanf("%d",&n);
for (i=1;i<=n;i++) scanf("%d",&v[i]);

for (i=1;i<n;i++)
 for (j=i+1;j<=n;j++) if (v[i]>v[j]) v[i]=v[j]+v[i]-(v[j]=v[i]);

for (i=1;i<n-1;i++)
 for (j=i+1;j<n;j++)
//  for (k=j+1;k<=n;k++)
{ k=j+1;
  while ((v[i]+v[j]>=v[k])&&(k<=n))
     {
     ct++;
     k++;
     }
}
printf("%ld",ct);
return 0;
}