#include <bits/stdc++.h>
using namespace std;
int arr[26];
int main() {
  long double r, x, y, xx, yy;
  cin >> r >> x >> y >> xx >> yy;
  long double dist = sqrt((x - xx) * (x - xx) + (y - yy) * (y - yy));
  cout << ceil(dist / (2.0 * r));
  return 0;
}
