def dec_to_bin(n):
    ans = 0
    f = 0
    n = int(n)
    while (n != 0):
        ans += ((10 ** f) * (n % 2))
        n = n // 2
        f += 1
    return ans

def bin_to_dec(n):
    ans = 0
    f = 0
    n = int(n)
    while (n != 0):
        ans += ((2 ** f) * (n % 10))
        n = n // 10
        f += 1
    return ans

def oct_to_dec(n):
    ans = 0
    f = 0
    n = int(n)
    while (n != 0):
        ans += ((8 ** f) * (n % 10))
        n = n // 10
        f += 1
    return ans

def hex_to_dec(n):
    ans = 0
    return 0