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