# https://yukicoder.me/problems/no/3578


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

    if B == 1:
        print(0)
    elif B % 2 == 0:
        x = (N - 1) % B
        if x % 2 == 0:
            print(x // 2)
        else:
            print("NaN")
    else:
        inv2 = pow(2, B - 2, B)
        ans = (N - 1) * inv2
        ans %= B
        print(ans)
            






if __name__ == "__main__":
    main()