#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  ;
  long double r, x, y, xn, yn;
  cin >> r >> x >> y >> xn >> yn;
  long double dist;
  dist = sqrt(pow(x - xn, 2) + pow(y - yn, 2));
  cout << ceil(dist / (2 * r));
  return 0;
}
