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#include <cstdio>
using namespace std;

long long int I64max;

long long int n, k;
long long int *L;
int Lmax;
char prev;

void putLower() {
    switch(prev) {
        case 'a':
            printf("b");
            prev='b';
            break;
        case 'b':
        case 'c':
            printf("a");
            prev='a';
            break;
    }
}
void putHigher() {
    switch(prev) {
        case 'c':
            printf("b");
            prev='b';
            break;
        case 'b':
            ;
        case 'a':
            printf("c");
            prev='c';
            break;
    }
}


int main() {

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

    I64max = 1;
    I64max <<= 61;
    L = new long long int [100];
    L[0] = 1 ;
    for( int i=1 ; L[i-1]<I64max && i<=n-1 ; i++ )
    {
        L[i] = 2*L[i-1]+1;
        Lmax = i;
    }

    if( n-1>Lmax || k<=L[n-1] ) {
        printf("a");
        prev = 'a';
    } else {
        k -= L[n-1];
        if( k<=L[n-1] ) {
            printf("b");
            prev = 'b';
        } else {
            k -= L[n-1];
            if( k<=L[n-1] ) {
                printf("c");
                prev = 'c';
            } else {
                printf("NIE\n");
                return 0;
            }
        }
    }

    for( int i=n-1 ; i>0 ; i-- ) {
        if( k==1 ) {
            printf("\n");
            return 0;
        }

        k--;
        if( i-1>Lmax ) {
            putLower();
        } else if( k>L[i-1] ) {
            k -= L[i-1];
            putHigher();
        } else {
            putLower();
        }
    }


    printf("\n");
    return 0;
}