#include <bits/stdc++.h>
using namespace std;
double r;
double dis(double x, double y, double a, double b) {
  return sqrt(((x - a) * (x - a) + (y - b) * (y - b)) / (r * r * 4.0));
}
int main() {
  double x, y;
  double a, b;
  double dd;
  scanf("%lf %lf %lf %lf %lf", &r, &x, &y, &a, &b);
  dd = dis(x, y, a, b);
  int ff = (int)ceil(dd);
  printf("%d\n", ff);
  return 0;
}
