# include <stdio.h>
int main (){
	int n,i,j,a[800],nr=0,aux;
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	scanf("%d",&n);
   if (n>=3)
	  {for(i=0;i<n;i++)
		     scanf("%d",&a[i]);
      for (i=1;i<n;i++)
         {aux=a[i];
          j=i-1;
          while (j>0 && aux<a[j])
               {a[j+1]=a[j]; j--;}
          if (aux>=a[j]) a[j+1]=aux;
                else
                 {a[1]=a[0]; a[0]=aux;}
          }
      for(i=0;i<n-2;i++)
      	for(j=i+2;j<n && a[j]<=a[i]+a[i+1];j++)
				if(a[i]+a[j]>a[i+1] && a[i+1]+a[j]>a[i])
					                     nr++;}
   printf("%d",nr);
	return 0;
}