#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int r;
  long int x, y, X, Y;
  cin >> r >> x >> y >> X >> Y;
  double d = sqrt((X - x) * (X - x) + (Y - y) * (Y - y));
  int residue;
  if (d - d / (2 * r) - (int)(d - d / (2 * r)) == 0)
    residue = 0;
  else
    residue = 1;
  long long int ans = (int)d / (2 * r) + residue;
  cout << ans;
  return 0;
}
