#include <bits/stdc++.h>
using namespace std;
int main() {
  double r, x1, y1, x2, y2;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  long long x =
      (long long)sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2)) / 2 / r;
  if (x * 2.0 * r < sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2)))
    cout << x + 1;
  else
    cout << x;
  return 0;
}
