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#include <bits/stdc++.h>

using namespace std;

#define PB push_back
#define FORE(i, t) for(__typeof(t.begin())i=t.begin();i!=t.end();++i)
#define SZ(x) int((x).size())
#define REP(i, n) for(int i=0,_=(n);i<_;++i)
#define FOR(i, a, b) for(int i=(a),_=(b);i<=_;++i)
#define FORD(i, a, b) for(int i=(a),_=(b);i>=_;--i)

typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> pii;

const int INF = 1e9 + 9;
const ll LLINF = 3e18 + 9;

ll F[70] = {0, 3}, max_F_id;
int next_char[4][3] = {
    {1, 2},
    {0, 2},
    {0, 1},
    {0, 1, 2},
};

void init_F() {
    for (int i = 2;;++i) {
        F[i] = 2LL * F[i - 1] + 3;
        if (F[i] > LLINF) {
            max_F_id = i;
            break;
        }
    }
}

ll f(int x) {
    if (x > max_F_id) {
        return F[max_F_id];
    }
    return F[x];
}

void reconstruct(int last, int n, ll k) {
//    cout << "last: " << last << " n: " << n << " k: " << k << "\n";
    for (;;) {
        if (k == 0) {
            return;
        }
        --k;
        ll third = f(n) / 3;
        int part = k / third;
        last = next_char[last][part];
        cout << "abc"[last];
        --n;
        k %= third;
    }
}

void inline one() {
    init_F();
    REP (i, 70) {
//        cout << i << ": " << f(i) << "\n";
    }
    int n;
    ll k;
    cin >> n >> k;
    if (k > f(n)) {
        puts("NIE");
        return;
    }
    reconstruct(3, n, k);
    cout << "\n";
}

int main() {
    ios::sync_with_stdio(false);
    //int z; cin >> z; while(z--)
    one();
}