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