题解 | #[NOIP1999]回文数#

a=int(input())
b=input()
num=0
while a==10 and b!=''.join([i for i in reversed(b)]):
    b=str(int(b)+int(''.join([i for i in reversed(b)])))
    num+=1
    if num>30:
        print('imposs')
        break
while a==2 and b!=''.join([i for i in reversed(b)]):
    b=bin(int(b,2)+int(''.join([i for i in reversed(b)]),2))[2:]
    num+=1
    if num>30:
        print('Impossible!')
        break
while a==16 and b!=''.join([i for i in reversed(b)]):
    b=hex(int(b,16)+int(''.join([i for i in reversed(b)]),16))[2:]
    num+=1
    if num>30:
        print('imposs')
        break
if num<=30:
    print('STEP=%d'%(num))