#include <iostream>
#include <fstream>
#include <cstring>
#include <cstdio>
using namespace std;

ifstream fin("nrtri.in");
ofstream fout("nrtri.out");

int m,p,u,V[100001],i,j,N;
int cautare(int p, int u)
{
  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))
    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;
}

int main()
{
fin>>N;
for (i=0; i<N-2; ++i)
{
    for (j=0; j<N-1; ++j)
    {
        cautare(1,N);
        m=m+i-j-1;
    }
}
fout<<m;

}