def solution(n):
rlt = []
while n > 1:
if n%3 == 0:
n -= 3
rlt.append(3)
else:
rlt.append(n%3)
n = n//3
if n > 0:
rlt.append(n)
temp = [str(x) if x!=3 else '4' for x in rlt]
return ''.join([temp[i] for i in range(len(temp)-1, -1, -1)])