#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x, y, xx, yy;
  cin >> r >> x >> y >> xx >> yy;
  long long dist = (x - xx) * (x - xx) + (y - yy) * (y - yy);
  long long a = 2 * r, c = 0;
  for (;;) {
    long long b = a * c;
    if (b * b >= dist) break;
    c++;
  }
  cout << c << endl;
  return 0;
}
