先转成10进制，再用10进制转成要的：

a,b = map(int,input().split())

number = input()

# 先变成10进制
number = int(number,a)

ans = ""

while number>0:
    mid = int(number%b)
    if mid>=10:
        mid = mid-10+ord('a')
        mid = chr(mid)
    ans = str(mid)+ans
    number = number/b
    if number<1:
        break

print(ans)