#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int r, x, y, xx, yy;
  cin >> r >> x >> y >> xx >> yy;
  r *= 2;
  xx -= x;
  yy -= y;
  x = 0;
  y = 0;
  double l = sqrt(xx * xx + yy * yy);
  cout << ceil(l / r) << endl;
}
