def four(n):
 
 if n - 4 != 0:
    
    if n % 10 == 0:
       four(n//10)
       #break
    elif n % 10 == 4:
       four(n//10)
      # break
    else:
       four(n*2)
    print(n, end=" -> ")

print("4 -> ", end = "")
four(147)