1516.cpp

#include <cstdio>
#include <cmath>
#include <algorithm>

void buildTree(int n1, int n2, int h) {
	int n = n2 - n1 + 1;
	if((n == 0) || (h == 0)) {
		return ;
	}

	int powerH = pow(2, h);
	if((n > 1) || (h > 1)) { 
		if(n > (powerH - 1)) {
			//printf("%d %d %d\n", n1, n2, h);
			printf(" Impossible.");
			return ;
		}
	}
	int goesToLeft = std::max(n - powerH / 2, 0);
	
	//printf("%d %d %d %d\n", n1, n2, h, goesToLeft);
	printf(" %d", n1 + goesToLeft);
	if(goesToLeft > 0) {
		buildTree(n1, n1 + goesToLeft - 1, h - 1);
	}
	buildTree(n1 + goesToLeft + 1, n2, h - 1);
}

int main() {
	int n, h;
	int caseNum = 0;
	do {
		caseNum++;
		scanf("%d %d", &n, &h);
		if(n == 0) 
			break;
		printf("Case %d:", caseNum);
		buildTree(1, n, h);
		printf("\n");
	} while(1);
	return 0;
}