#include <bits/stdc++.h>
using namespace std;
int main() {
  double r, x, y, x1, y1;
  scanf("%lf%lf%lf%lf%lf", &r, &x, &y, &x1, &y1);
  double d = sqrt((x1 - x) * (x1 - x) + (y1 - y) * (y1 - y));
  double a = 2 * r;
  int ans = d / a;
  if (ans * a < d) ans++;
  printf("%d\n", ans);
  return 0;
}
