#include <bits/stdc++.h>
using namespace std;
long long r, x, y, xx, yy;
inline long long sqr(long long x) { return x * x; }
int main() {
  cin >> r >> x >> y >> xx >> yy;
  double d = sqrt(sqr(x - xx) + sqr(y - yy));
  long long ans = floor(d * 1.0 / (2 * r));
  if (ans * 2 * r < d) ans++;
  cout << ans << endl;
  return 0;
}
