#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x, y, x1, y1;
  cin >> r >> x >> y >> x1 >> y1;
  int sum = (x - x1) * (x - x1);
  int sum2 = (y - y1) * (y - y1);
  int sum3 = sum + sum2;
  cout << ceil((sqrt(sum3) / (2 * r))) << endl;
  return 0;
}
