#include <bits/stdc++.h>
using namespace std;
unsigned long int distance(long long int x0, long long int y0, long long int x,
                           long long int y) {
  unsigned long int ans = ceil(sqrt((x - x0) * (x - x0) + (y - y0) * (y - y0)));
  return ans;
}
int find_min(int r, int x0, int y0, int x, int y) {
  unsigned long int dist =
      distance((long int)x0, (long int)y0, (long int)x, (long int)y);
  long int number = ceil((long double)dist / (2 * r));
  return (int)number;
}
int main() {
  int r, x0, y0, x, y;
  cin >> r >> x0 >> y0 >> x >> y;
  int ans = find_min(r, x0, y0, x, y);
  cout << ans;
}
