#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int x, x2, y, y2, l, a, r, ans = 0;
  scanf("%lld %lld %lld %lld %lld", &r, &x, &y, &x2, &y2);
  ans =
      ceil((sqrt((x2 - x) * (x2 - x) + (y2 - y) * (y2 - y))) / (2 * r)) + 1e-9;
  cout << ans << endl;
  return 0;
}
