#include<fstream.h>

long i,j,k,n,a[1000],dif,s,nr;

int main()
{
 ifstream f("nrtri.in");
 ofstream g("nrtri.out");
 f>>n;
 for(i=1;i<=n;i++)f>>a[i];
 for(i=1;i<=n-2;i++)
  for(j=i+1;j<=n-1;j++)
   {
    if(a[i]>a[j])dif=a[i]-a[j];
    else dif=a[j]-a[i];
    s=a[i]+a[j];
    for(k=j+1;k<=n;k++)
     if(dif<=a[k]&&a[k]<=s)nr++;
    }
 g<<nr;
 return 0;
 }