#include <bits/stdc++.h>
using namespace std;
int main() {
  long r, x, y, a, b, j = 0, d;
  cin >> r >> x >> y >> a >> b;
  d = sqrt(((x - a) * (x - a)) + ((y - b) * (y - b)));
  j = d / r;
  if (d % r != 0) j++;
  j = (j > 0) ? j - 1 : 0;
  cout << j << endl;
  return 0;
}
