题解 | 好串

def check(cur):
    if len(cur) % 2 != 0 and cur.count('a') != cur.count('b'): 
        return 'Bad'
    if cur[0] != 'a' or cur[-1] != 'b':
        return 'Bad'
    for i in range(len(cur)//2):
        cur = cur.replace('ab', '')
    if cur != '':
        return 'Bad'
    return 'Good'

    
cur = input()
print(check(cur))