#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x, y, x1, y1;
  scanf("%d %d %d %d %d", &r, &x, &y, &x1, &y1);
  long long p = 1LL * (x1 - x) * (x1 - x) + 1LL * (y1 - y) * (y1 - y);
  long long res = (long long)ceil(sqrt(p / (4.0 * r * r)));
  cout << res << "\n";
}
