def tree(s1, s2):
    if len(s1) <= 1:
        print(s1, end='')
        return
    item = s2[len(s2)-1]
    print(item, end='')
    t1 = s1[:s1.index(item)]
    t2 = s1[s1.index(item)+1:]
    line = -1
    for i in s2:
        if i in t1:
            line += 1
        else:
            break
    tree(t1, s2[:line+1])
    tree(t2, s2[line+1:len(s2)-1])


str1 = input()
str2 = input()
tree(str1, str2)

显示输出了一个ASCII值为13的字符（回车？？？）