#include <bits/stdc++.h>
int main() {
  double r, x1, x2, y1, y2;
  scanf("%lf %lf %lf %lf %lf", &r, &x1, &y2, &x2, &y2);
  double dis = sqrt((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1));
  double m, d = 2 * r;
  int ans = 0;
  ans = dis / d;
  if (dis - d * ans > 1e-6) ans++;
  printf("%d\n", ans);
}
