#include "fstream"
std::ifstream in("nrtri.in");
std::ofstream out("nrtri.out");
int poz1,poz2;
int cautareBinara(int vect[],int val1,int val2,int stanga,int dreapta)
{
    int gasit=0;
      while (stanga <= dreapta&&gasit<2) {
            int mijloc = (stanga + dreapta) / 2;
            if (vect[mijloc]<=val1+val2&&vect[mijloc+1]>val1+val2)
                  {poz1=mijloc+1;gasit++;}
                  else if(vect[mijloc]+val1>=val2&&vect[mijloc-1]+val1<val2)
                  {poz2=mijloc-1;gasit++;}
            else if (vect[mijloc] > val1+val2)
                  dreapta = mijloc - 1;
            else
                  stanga = mijloc + 1;
      }
      if(gasit==2)
      return 1;
      else
      return 0;
}
void qSort(int vect[], int stanga, int dreapta) {
      int i = stanga, j = dreapta;
      int tmp;
      int pivot = vect[(stanga + dreapta) / 2];
      while (i <= j) {
            while (vect[i] < pivot)
                  i++;
            while (vect[j] > pivot)
                  j--;
            if (i <= j) {
                  tmp = vect[i];
                  vect[i] =vect[j];
                  vect[j] = tmp;
                  i++;
                  j--;
            }
      };
      if (stanga < j)
            qSort(vect, stanga, j);
      if (i < dreapta)
            qSort(vect, i, dreapta);
}
int main ()
{
	int k=0,n,i,j;
	in>>n;
	int *a=new int[n];
	for(i=0;i<n;i++)
		in>>a[i];
	qSort(a,0,n-1);
	for(i=0;i<n-1;i++)
		for(j=i+1;j<n;j++)
			if(cautareBinara(a,a[i],a[j],0,n-1)>0)
				k+=poz1-poz2-1;
	out<<k;
	in.close ();
	out.close ();
	return 0;
}