#include <bits/stdc++.h>
using namespace std;

char a[13][14];

set<pair<char, char>> s;
bool dfs(int i, int j) {
    if (j == 13) {
        return dfs(i + 1, 0);
    } else if (i == 13) {
        return true;
    } else {
        for (int x = 0; x < 13; ++x) {
            a[i][j] = x + (i & 1) * 13 + 'a';
            if (i and s.find({a[i - 1][j], a[i][j]}) != s.end())
                continue;
            if (j and s.find({a[i][j - 1], a[i][j]}) != s.end())
                continue;
            if (i) s.emplace(a[i - 1][j], a[i][j]);
            if (j) s.emplace(a[i][j - 1], a[i][j]);
            if (dfs(i, j + 1)) return true;
            if (i) s.erase({a[i - 1][j], a[i][j]});
            if (j) s.erase({a[i][j - 1], a[i][j]});
        }
        return false;
    }
}

int main() {
    cin.tie(nullptr)->sync_with_stdio(false);
    cout << 13 << '\n';
    assert(dfs(0, 0));
    for (int i = 0; i < 13; ++i)
        cout << a[i] << '\n';
    return 0;
}