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