from collections import deque

def find_nth_number(n):
    if not isinstance(n,int) :
        return "null"
    
    if n<=0:
        return "Invaild Input"
    queue= deque(["3","4"])
    count=0
    
    while queue:
       num=queue.popleft()
       count+=1
       
       if count==n:
            return num
       queue.append(num+"3")
       queue.append(num+"4")
       
       
def main():
    user_input=input().strip()
    
    if not user_input.isdigit():
        print("null")
        return
    
    n=int(user_input)
    print(find_nth_number(n))
    


if __name__=="_main_":
    main()