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