#include <bits/stdc++.h>
using namespace std;
int main() {
  long int y2;
  double r, x, y, x1, y1, ans, x2;
  cin >> r >> x >> y >> x1 >> y1;
  ans = sqrt(((x - x1) * (x - x1)) + ((y - y1) * (y - y1)));
  x2 = ans / (r * 2);
  y2 = ans / (r * 2);
  if ((x2 - y2) != 0) y2++;
  cout << y2 << endl;
  return 0;
}
