#include <bits/stdc++.h>
struct instrument {
  int days;
  int pos;
};
bool comp(instrument a, instrument b) { return a.days < b.days; }
int main() {
  int r, x0, y0, x1, y1;
  std::cin >> r >> x0 >> y0 >> x1 >> y1;
  long long a = (x0 - x1);
  a *= (x0 - x1);
  long long b = (y0 - y1);
  b *= (y0 - y1);
  float dist = sqrt(a + b);
  std::cout << ceil((dist / (2 * r)));
  return 0;
}
