#include <bits/stdc++.h>
using namespace std;
int main() {
  int r;
  cin >> r;
  double a, b, c, d;
  cin >> a >> b >> c >> d;
  double t = sqrt(pow(abs(a - c), 2) + pow(abs(b - d), 2));
  int t1 = ceil(t) / (2 * r);
  int t2 = ceil(t);
  t2 %= (2 * r);
  if (t2 > 0) t1++;
  cout << t1;
  return 0;
}
