题解 | #进制转换#(最易于理解的方法之一)

str1 = input()
str2 = str1[2:]
num1 = 0
num2 = len(str2) - 1
for i in str2:
    if i == "a" or i == "A":
        i = 10
    elif i == "b" or i == "B":
        i = 11
    elif i == "c" or i == "C":
        i = 12
    elif i == "d" or i == "D":
        i = 13
    elif i == "e" or i == "E":
        i = 14
    elif i == "f" or i == "F":
        i = 15
    num1 += (16 ** num2) * int(i)
    num2 -= 1
print(num1)