#include <bits/stdc++.h>
using namespace std;
int main() {
  double x1, x2, y1, y2, r;
  scanf("%lf", &r);
  scanf("%lf", &x1);
  scanf("%lf", &y1);
  scanf("%lf", &x2);
  scanf("%lf", &y2);
  r = 2 * r;
  double dis = (x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2);
  dis = sqrt(dis);
  double temp = fmod(dis, r);
  int ans = 0;
  if (temp > 0.0000000001) {
    ans = 1;
  }
  double Steps = dis / r;
  int steps = (int)Steps;
  ans = ans + steps;
  printf("%d\n", ans);
  return 0;
}
