#include <bits/stdc++.h>
using namespace std;
int main() {
  double r, a, b, a1, b1, out, d, aa, bb, R;
  cin >> r >> a >> b >> a1 >> b1;
  if (a == a1 && b == b1)
    cout << 0;
  else {
    aa = a1 - a;
    bb = b1 - b;
    aa = aa * aa;
    bb = bb * bb;
    d = sqrt(aa + bb);
    R = 2 * r;
    out = (d / R);
    cout << ceil(out);
  }
}
