#include <iostream>
#include <string>
using namespace std;

const int MAXSIZE = 62;
long long upper[MAXSIZE+1];
long long p2[MAXSIZE];

void init()
{
	upper[0] = 0;
	upper[1] = 1;
	for(int i=2; i<=MAXSIZE; i++) {
		upper[i] = upper[i-1] + 2*upper[i-2] + 3;
	}
	p2[0] = 1;
	for(int i=1; i<MAXSIZE; i++)
		p2[i] = 2*p2[i-1];
}

string convert(long long a, int len)
{
	string s = "";
	for(int i=0; i<len; i++) {
		if (a%2 == 0)
			s = "a"+s;
		else
			s = "b"+s;
		a /= 2;
	}
	return s;
}

string getString(long long n)
{
	int len = 1;
	while (upper[len] < n)
		len++;
	long long base = upper[len-1]+1;
	int j = len-1;
	string s = "";
	while (j >= 0) {
		if (n < base+p2[j]) {
			s += "a"+convert(n-base, j);
			break;
		}
		s += "bb";
		base += p2[j];
		j -= 2;
	}
	return s;
}

int main()
{
	long long n, m;
	int icase = 0;
	init();

	cin >> n >> m;
	while (n != 0) {
		string s1 = getString(1+n*(m-1));
		string s2 = getString(n*m);
		cout << "Case " << ++icase << ": " << s1 << ' ' << s2 << endl;
		cin >> n >> m;
	}
}