#include <bits/stdc++.h>
using namespace std;
int main() {
  std::ios::sync_with_stdio(false);
  double r, a, b, c, d;
  cin >> r >> a >> b >> c >> d;
  double dist = sqrt((c - a) * (c - a) + (d - b) * (d - b));
  double moves = dist / (2 * r);
  int move = moves;
  if (moves > move) {
    cout << move + 1;
  } else {
    cout << move;
  }
}
