1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
#include <cstdio>
#include <string>
#include <iostream>
using namespace std;

char next(char f) {
	switch(f) {
		case 'a': return 'b';
		case 'b': return 'a';
		case 'c': return 'a';
		default: return 'a';
	}
}

char next2(char f) {
	switch(f) {
		case 'a': return 'c';
		case 'b': return 'c';
		case 'c': return 'b';
		default: return 'b';
	}
}

string A;

void generate(long long n, long long k, char f) {
	//printf("%c %lld %lld\n", f, n, k);
	if(k == 0)
		return;
	if(n == 0) {
		if(k > 0) 
			A = "NIE";
		return;
	}
	if (n > 62 || (k < 1ll << n)) {
		A.push_back(next(f));
		generate(n - 1, k - 1, next(f));
	}
	else {
		k -= (1ll << n) - 1;
		A.push_back(next2(f));
		generate(n - 1, k - 1, next2(f));
	}
	
}

int main() {
	int n;
	long long k;
	scanf("%d%lld", &n, &k);
	generate(n, k, ' ');
	cout << A << "\n";
}