#include <cstdio>

int main()
{
 FILE* f=fopen("nrtri.in","r");
 int n;
 fscanf(f,"%d",&n);
 int a[n+1];
 for (int i=1;i<=n;i++)
{
    fscanf(f,"%d",&a[i]);
}
 int db=0;
 fclose(f);
 f=fopen("nrtri.out","w");
 for(int i=1;i<=n-2;i++)
 {

 for (int j=i+1;j<=n-1;j++)
 {
             for (int q=j+1;q<=n;q++)
        {
            if((a[i]+a[j]>=a[q])&&((a[i]+a[q]>=a[j])&&(a[q]+a[j]>=a[i]))) db++;
        }
 }
 }
  fprintf(f,"%d",db);
  fclose(f);
}