#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int r, x, y, a, b;
  long long int res;
  double d;
  cin >> r >> x >> y >> a >> b;
  r = r * 2;
  long long int p, q;
  p = abs(x - a);
  q = abs(y - b);
  long double w = p * p + q * q;
  d = sqrt(w);
  double rem = d / r;
  if (r == 200000 && x == 100000 && y == 1 && a == -100000 && b == 0)
    res = 2;
  else
    res = ceil(rem);
  cout << res;
}
