#include <bits/stdc++.h>
using namespace std;
double dist(int x1, int y1, int x2, int y2) {
  return sqrt(pow((x1 - x2), 2) + pow((y1 - y2), 2));
}
int main() {
  int r, x, y, x1, y1;
  cin >> r >> x >> y >> x1 >> y1;
  double d = dist(x, y, x1, y1);
  int p = d;
  if (p == d && p % (2 * r) == 0) {
    cout << p / (2 * r);
  } else {
    cout << (int)d / (2 * r) + 1;
  }
}
