def main():
    N, A, B = map(int, input().split())

    if 4*A-2*B <= 0:
        print((N-1)*A - N*B)
        return

    if N % 2 == 1:
        print(-(N-1)*A - B)
    else:
        print(-(N-1)*A)


if __name__ == "__main__":
    main()