#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int r, x, y, x1, y1;
  long double a, b, c, d, e;
  cin >> r >> x >> y >> x1 >> y1;
  c = (pow((x1 - x), 2));
  d = (pow((y1 - y), 2));
  a = sqrt(c + d);
  e = (a / (2 * r));
  b = ceil(e);
  cout.setf(ios::fixed);
  std::cout << std::setprecision(0) << b;
}
