题解 | #进制转换#

num = input()[2:]
ls = list(map(str, num))
n16 = "0123456789ABCDEF"
di = {}
for n, j in enumerate(n16):
    di[j] = n
res = 0
for n, i in enumerate(ls[::-1]):
    res += (16 ** n) * di[i]
print(res)