class Solution:
def solve(self , M: int, N: int) -> str:
# book = {10:'A', 11:'B', 12:'C', 13:'D', 14:'E', 15:'F'}
book = '0123456789ABCDEF'
ret = []
sign = '-' if M < 0 else ''
rest = abs(M)
while rest:
r = rest % N
# ret.append(str(book.get(r, r)))
ret.append(book[r])
rest //= N
return sign + ''.join(ret[::-1])