#include<fstream.h>

int v[100],n,k=0,i,j;

ifstream f("nrtri.in");
ofstream g("nrtri.out");

int cautare(int p, int u);

int main()
{
	f>>n;
	for(i=0;i<n;i++)
		f>>v[i];
	for (i=0;i<n-2;++i)
    		for (j=0;j<n-1;++j)
			k=cautare(1,n)-1;

	g<<k;
	

return 0;
}
int cautare(int p, int u)
{
  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;
}