#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  double a, b, res = 10e15, speed = 0;
  double x, y, v, r;
  cin >> r >> a >> b >> x >> y;
  double test = sqrt((pow((a - x), 2)) + (pow((b - y), 2)));
  cout << ceil(test / (r * 2)) << endl;
  return 0;
}
