#include <bits/stdc++.h>
using namespace std;
double tick() {
  static clock_t oldt, newt = clock();
  double diff = 1.0 * (newt - oldt) / CLOCKS_PER_SEC;
  oldt = newt;
  return diff;
}
int main() {
  int r, x, y, x1, y1;
  cin >> r >> x >> y >> x1 >> y1;
  cout << ceil(sqrt(pow(y1 - y, 2) + pow(x1 - x, 2)) / (2 * r)) << "\n";
  cerr << "execution time is: " << tick() << "\n";
}
