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

typedef long long ll;

const ll inf = 1000000000000000005LL;
const int maxn = 1000005;

ll d[maxn];

void print(int j) {

    static int last = 3;

    char next[][3] = {{'b', 'c', '\0'}, {'a', 'c', '\0'}, {'a', 'b', '\0'}, {'a', 'b', 'c'}};
    char c = next[last][j];

    putchar(c);
    last = c - 'a';
}

void printSolution(int n, ll k) {

    d[n] = 1;

    for(int i = n - 1; i >= 1; --i) {

        d[i] = min(inf, d[i + 1] * 2 + 1);
    }

    if(k > d[1] * 3) {

        printf("NIE");
    }
    else {

        int j = 0;

        while(j < 3 && k > d[1]) {

            k -= d[1];
            j++;
        }

        print(j);

        for(int i = 2; i <= n; ++i) {

            if(--k == 0)
                return;

            j = (k > d[i]);

            if(j) k -= d[i];

            print(j);
        }
    }
}

int main() {

    ll k;
    int n;

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

    printSolution(n, k);
    printf("\n");
}