#include "fstream"
std::ifstream in("nrtri.in");
std::ofstream out("nrtri.out");
int n;
int cautare(int v[],int i,int j)
{
int p=0,u=n-1;
  int m;
  m=(p+u)/2;
  while (p<=u){
      if ((v[m]<=v[i]+v[j] && v[m+1]>v[i]+v[j]) || (v[m]<=v[i]+v[j] && m==n-1))
		  return m;
	  else if (v[m]<=v[i]+v[j] && v[m+1]<=v[i]+v[j]) {
		  p=m+1;
		  m=(p+u)/2;
	  }
	  else {
		  u=m-1;
		  m=(p+u)/2;
		  }
  }
  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,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(cautare(a,i,j))
				k++;
	out<<k;
	in.close ();
	out.close ();
	return 0;
}