#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x, y, x1, y1;
  cin >> r >> x >> y >> x1 >> y1;
  double dis = sqrt((x - x1) * (x - x1) + (y - y1) * (y - y1));
  double ans1 = dis / (2 * r);
  long long int ans = ans1;
  if (ans1 != ans) {
    ans++;
  }
  cout << ans << endl;
  return 0;
}
