#include <bits/stdc++.h>
using namespace std;
long double r, x, y, x2, y2;
int main() {
  cin >> r >> x >> y >> x2 >> y2;
  long double d = sqrt((x - x2) * (x - x2) + (y - y2) * (y - y2));
  long double k = d / (2 * r);
  long double k2 = (long double)(int)(k);
  if (k > k2) k += 1.0;
  long double k3 = k;
  cout << ((int)round(k) - (round(k) > k));
  return 0;
}
