#include <iostream>

#include <math.h>

#include <stdio.h>

#include <cstdio>

#include <algorithm>

#include <string.h>

#include <cstring>

#include <queue>

#include <vector>

#include <functional>

#include <cmath>

#define SCF(a) scanf("%d", &a)

#define IN(a) cin>>a

#define FOR(i, a, b) for(int i=a;i<b;i++)

typedef long long Int;

using namespace std;

void order(int start, int end, int height)

{

	if (start > end)

		return;

	if (height == 0)

		printf(" %d", start);

	else

	{

		int n = pow(2, height - 1) - 1;

		int num = end - start + 1;

		if (num > n)

		{

			int root = end - n;

			printf(" %d", root);

			order(start, root - 1, height - 1);

			order(root + 1, end, height - 1);

		}

		else

		{

			printf(" %d", start);

			order(start+1, end, height - 1);

		}

	}

}

int main()

{

	int N, H;

	int t = 1;

	while (SCF(N) && SCF(H))

	{

		if (N == 0 && H == 0)

			break;

		if (H < floor(log2(N) + 1))

			printf("Case %d: Impossible.\n", t++);

		else

		{

			printf("Case %d:", t++);

			if (H > N)

				H = N;

			order(1, N, H);

			printf("\n");

		}

	}

	return 0;

}