#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x, y, z, t;
  cin >> r >> x >> y >> z >> t;
  double d = sqrt(pow(x - z, 2) + pow(y - t, 2));
  int l = d;
  if (d - l / (2 * r) * 2 * r == 0) {
    cout << l / (2 * r);
  } else
    cout << (l / (2 * r) + 1) << endl;
  return 0;
}
