#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x1, y1, x2, y2;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  double dist = sqrt((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1));
  long long int count = (long long int)(dist / (2 * r));
  long double diff = dist - count * 2 * r;
  if (diff > r) count = count + 2;
  if (diff < r && diff > 0) count++;
  cout << count;
}
