# 方法1
line = input()
line = line[2:]

dic = dict(zip(list("0123456789ABCDEF"), range(0, 16)))

ret = 0
for i, char in enumerate(line):
    ret += dic[char] * 16 ** (len(line) - 1 - i)
print(ret)


# 方法2
# print(int(input(), 16))