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#include <vector>
#include <list>
#include <map>
#include <set>
#include <queue>
#include <deque>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <ctime>
#include <cstring>
#include <cassert>

#define FOR(i,b,e) for(int i=(b);i<(e);++i)
#define FORQ(i,b,e) for(int i=(b);i<=(e);++i)
#define FORD(i,b,e) for(int i=(b)-1;i>=(e);--i)
#define REP(x, n) for(int x = 0; x < (n); ++x)

#define PB push_back
#define LL long long
#define MP make_pair
#define ST first
#define ND second

using namespace std;

#define MR 1000010

LL k;

int n, pos, prevV;

void go()
{
    if (!k)
        return;

    assert( pos <= n );

    LL val = ( n - pos + 1 >= 62 ? 1LL << 62 : 1LL << ( n - pos + 1 ) ) - 1;

    if (val < k)
    {
        k -= val;
        if (val < k)
        {
            assert( prevV == -1 );
            k -= val;
            if (val < k)
                printf( "NIE" );
            else
            {
                printf("c");
                pos++;
                k--;
                prevV = 2;
                go();
            }
        }
        else
        {
            char first = prevV == 2 ? 'b' : 'c';
            printf( "%c", first );
            pos++;
            k--;
            prevV = first - 'a';
            go();
        }
    }
    else
    {
        char first = prevV ? 'a' : 'b';
        printf( "%c", first );
        pos++;
        k--;
        prevV = first - 'a';
        go();
    }
}

int main() {
    scanf( "%d%lld", &n, &k );
    pos = 1;
    prevV = -1;
    go();
    printf( "\n" );
    return 0;
}