def from_base(digits, base):
    power = 1
    number = 0
    for digit in reversed(digits):
        number += power * digit
        power *= base
    return number
    
digits = [int(input("digit_a : ")), int(input("digit_b : ")), int(input("digit_c : ")), int(input("digit_c : "))]
base = int(input("base : "))

print(from_base(digits, base))