#include <bits/stdc++.h>
using namespace std;
bool num(double n) {
  if ((n - (int)n) > 0)
    return true;
  else
    return false;
}
int main() {
  double r, x, y, x1, y1, s;
  cin >> r >> x >> y >> x1 >> y1;
  s = sqrt((x - x1) * (x - x1) + (y - y1) * (y - y1));
  s /= 2 * r;
  if (num(s)) {
    s += 1;
    cout << setprecision(0) << s;
  } else
    cout << s;
  return 0;
}
