#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x, y, x1, y1;
  cin >> r >> x >> y >> x1 >> y1;
  double u = pow(pow(x - x1, 2) + pow(y - y1, 2), 0.5);
  if (x - x1 == 0 && y - y1 == 0) {
    cout << "0";
    return 0;
  }
  int m = 2 * r, s = 0;
  while (m < u) {
    m += 2 * r;
    s++;
  }
  cout << s + 1;
  return 0;
}
