def main(a):
    numbers = {
        10: "A",
        11: "B",
        12: "C",
        13: "D",
        14: "E",
        15: "F"
    }
    if a >= 0:
        return hex(a)[2:].upper()
    else:
        answer_hex = hex(abs(a))[2:]
        if len(answer_hex) % 2 != 0:
            answer_hex += "0"
        answer = ""
        for i in answer_hex:
            if 15 - int(i) > 9:
                answer += numbers[15 - int(i)]
            else:
                answer += str(15 - int(i))
        answer = hex(int(answer[::-1], 16) + 1)[2:].upper()
        return answer

print(main(-1))