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#include <bits/stdc++.h>
#include <math.h>
using namespace std;

char slowo[1000001];

int main() {
    int n;
    long long k;

    scanf("%d %lld", &n, &k);

    long double p = 1;

    long double akt = 0;

    long double pot2 = 1;

    int length = 0;

    for(int i = 0; i < n - 1; i++) {
        pot2 *= 2;
    }

    long double cos = 1;

    for(int i = 0; i < n; i++) {
        akt += pot2 / cos;
        cos *= 2;
    }

    long double z = akt;

    if(k <= akt) {
        slowo[length] = 'a';
        length++;
    }
    else if(k > akt && k <= akt*2) {
        slowo[length] = 'b';
        p = akt + 1;
        length++;
        z = akt*2;
    }
    else if(k > akt*2 && k <= akt*3) {
        slowo[length] = 'c';
        p = akt * 2 + 1;
        length++;
        z = akt*3;
    }
    else {
        printf("NIE");
        return 0;
    }

    while(p < z) {
        if(k == p) {
            break;
        }

        p++;

        long double s = floor((p + z)/2);

        //cout<<p<<" "<<s<<" "<<z<<" "<<slowo[length - 1]<<endl;

        if(k > s) {
            if(slowo[length - 1] == 'a') {
                slowo[length] = 'c';
            }
            if(slowo[length - 1] == 'b') {
                slowo[length] = 'c';
            }
            if(slowo[length - 1] == 'c') {
                slowo[length] = 'b';
            }

            p = s + 1;
        }
        else if(k <= s) {
            if(slowo[length - 1] == 'a') {
                slowo[length] = 'b';
            }
            if(slowo[length - 1] == 'b') {
                slowo[length] = 'a';
            }
            if(slowo[length - 1] == 'c') {
                slowo[length] = 'a';
            }

            z = s;
        }

        length++;
    }

    for(int i = 0; i < length; i++) {
        printf("%c", slowo[i]);
    }

    printf("\n");

    return 0;
}