#include <bits/stdc++.h>
using namespace std;
double r, x, y, xx, yy;
int main() {
  cin >> r >> x >> y >> xx >> yy;
  double d = sqrt((x - xx) * (x - xx) + (y - yy) * (y - yy));
  int x = d / (r + r);
  if ((r + r) * x + 1e-8 < d) ++x;
  cout << x << endl;
  return 0;
}
