#include <bits/stdc++.h>
using namespace std;
int main() {
  double r, x1, y1, x2, y2;
  scanf("%lf%lf%lf%lf%lf", &r, &x1, &y1, &x2, &y2);
  printf("%d\n", (int)ceil(sqrt(pow(x1 - x2, 2) + pow(y1 - y2, 2)) / (2 * r)));
  return 0;
}
