#
# This program reads in a base (between 2 and 36 inclusive)
# and a number, and converts the number in that base to decimal
# It then asks the user for an output base, and converts that
# number to that base
#
# Matt Bishop    ECS 36A, Winter 2019
#
# digits for base 36
#
cvtdigits = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"   

#
# convert number to decimal
#
def baseto10(ibase, num):
    # assume no error and initialize the accumulator
    err = False
    decnum = 0
    # now loop, processing num
    for i in num:
        # convert the dgit to an integer
        # we do it this way because the
        # digita and letters (for > 9) are
        # not contiguous
        digval = cvtdigits.find(i)
        # oops ... error; say so but keep going
        # so you can identify all bad digits
        if digval == -1 or digval >= ibase:
            print("Invalid digit:", i)
            err = True
            continue
        # good digit ... add it in
        decnum = digval + decnum * ibase

    #
    # return what you got and whether there was an error
    #
    return err, decnum

#
# convert number from decimal
#
def basefrom10(obase, num):
    # starting string; the digita accumulate here
    out = ""
    # loop until you're done with the number
    while num > 0:
        # get the integer value of the last digit
        digval = num % obase
        # put it at the *front* of the current number
        out = cvtdigits[digval] + out
        # move on to the next digit
        num = num // obase

    # return the string
    return out
#
# read in a base
# it *must* be an integer between 2 and 36 inclusive
# as those are the bases for which we have digits
#
def readbase(prompt):
    # we catch everything here
    try:
        # get the base
        base = int(input(prompt))
    except (EOFerror, KeyboardInterrupt):
        # all done!
        return -1
    except Exception as msg:
        # unknown exception -- say what it is and give up
        print(msg)
        return -1
    #
    # we have input as an integer; be sure the integer is valid
    #
    if base < 2 or base > 36:
        print("Invalid base"+str(base)+"; must be between 2 and 36 inclusive")
        return -1
    # it is -- return it
    return base

def main():
    #
    # read in the number, removing blanks
    #
    num = input("Number to be converted: ")
    num = num.strip()
    #
    # read the input base 
    #
    inbase = readbase("Input base: ")
    if inbase == -1:
        return
    #
    # convert it to base 10
    # errot is True if there was a problem; if so, quit
    #
    error, decnum = baseto10(inbase, num)
    if not error:
        #
        # okay, it's good -- print out the number
        #
        #print(num, "in base", inbase, "is", decnum, "in decimal")
        #
        # get the output base; EOF ends it all
        #
        outbase = readbase("Output base (EOF to quit): ")
        if outbase != -1:
            print(basefrom10(outbase, decnum))


main()