LitereGen1

#include <iostream>
#include <cmath>
using namespace std;

char st [20];
int n;

int check (int k)
{
    if (abs (st [k] - st [k - 1]) > 1)
        return 0;

    if (st [k] == st [k - 1])
        return 0;

    if (k == n - 2)
        if (abs (st [k] - st [n - 1]) > 1)
            return 0;

    return 1;
}

void back (int k)
{
    for (char i = 'a'; i <= 'z'; i ++)
    {
        st [k] = i;
        if (check (k))
        {
            if (k == n - 2)
                cout << st << "\n";
            else
                back (k + 1);
        }
    }
}

int main()
{
    cin >> n;
    st [0] = 'a';
    st [n - 1] = 'a';
    back (1);
    return 0;
}