#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x, y, x1, y1;
  float d;
  cin >> r >> x >> y >> x1 >> y1;
  d = sqrt((abs(x - x1) * abs(x - x1)) + (abs(y - y1) * abs(y - y1)));
  cout << ceil(float(d) / (2 * r));
  return 0;
}
