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#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;

typedef long long int lint;

const lint MAX_K = 1000000000000000000LL;

lint pow2(int exp) {
    if (exp > 62)
        return 2 * MAX_K;
    lint res = 1;
    while(exp--) {
        res *= 2;
    }
    return res;
}

char first(char c) {
    switch(c) {
        case 'a':
            return 'b';
        case 'b':
            return 'a';
        case 'c':
            return 'a';
        default:
            throw "Error in `first`";
    }
}

char second(char c) {
    switch(c) {
        case 'a':
            return 'c';
        case 'b':
            return 'c';
        case 'c':
            return 'b';
        default:
            throw "Error in `first`";
    }
}

string solve(int n, lint k, string prefix) {
    int l = prefix.size();
    lint subtreeSize = pow2(n - l) - 1;
    if (l == 0) {
        if (k <= subtreeSize)
            return solve(n, k, "a");
        else if (k <= 2*subtreeSize)
            return solve(n, k - subtreeSize, "b");
        else
            return solve(n, k - 2*subtreeSize, "c");
    }
    if (k == 1)
        return prefix;
    if (n == l)
        return "NIE";
    if (subtreeSize >= k-1)
        return solve(n, k-1, prefix + first(prefix[l-1]));
    else
        return solve(n, k - 1 - subtreeSize, prefix + second(prefix[l-1]));
}
int main() {
    int n;
    lint k;
    cin >> n >> k;
    cout << solve(n, k, "") << endl;
}