public static void main(String[] args) {
System.out.println("求第几个丑数");
int n = new Scanner(System.in).nextInt();
long ugly = chouShu(n);
System.out.println(ugly);
}
private static long chouShu(int n) {
LinkedList<Long> list3 = new LinkedList<>();
LinkedList<Long> list5 = new LinkedList<>();
LinkedList<Long> list7 = new LinkedList<>();
list3.add(3L);//
list5.add(5L);
list7.add(7L);
long r = 0;
for(int i=1; i<=n; i++) {
long a = list3.getFirst();
long b = list5.getFirst();
long c = list7.getFirst();
r = Math.min(a, Math.min(b, c));
if(r == a) list3.removeFirst();
if(r == b) list5.removeFirst();
if(r == c) list7.removeFirst();