#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, cx, cy, x, y;
  cin >> r >> cx >> cy >> x >> y;
  long long int ans = pow((cx - x), 2) + pow((cy - y), 2);
  long double res = sqrt(ans);
  cout << ceil(res / (float)(2 * r)) << endl;
  return 0;
}
