#include <bits/stdc++.h>
using namespace std;
int main() {
  double r, x, y, wanted_x, wanted_y;
  scanf("%lf%lf%lf%lf%lf", &r, &x, &y, &wanted_x, &wanted_y);
  int steps =
      sqrt((x - wanted_x) * (x - wanted_x) + (y - wanted_y) * (y - wanted_y)) /
      (2 * r);
  double temp =
      sqrt((x - wanted_x) * (x - wanted_x) + (y - wanted_y) * (y - wanted_y)) /
      (2 * r);
  if (steps != temp) steps++;
  printf("%d", steps);
  return 0;
}
