#include <bits/stdc++.h>
using namespace std;
bool checker(int n, vector<vector<char>> a) {
	set<string> s;
	for (int i = 0; i < n; ++i)
		for (int j = 0; j < n; ++j) {
			string str(1, a[i][j]);
			for (int k = j + 1; k < n; ++k)
				str += a[i][k], s.insert(str);
		}
	for (int j = 0; j < n; ++j)
		for (int i = 0; i < n; ++i) {
			string str(1, a[i][j]);
			for (int k = i + 1; k < n; ++k)
				str += a[k][j], s.insert(str);
		}
	return (int) s.size() == n * n * (n - 1);
}
int main() {
	mt19937 eng(chrono::steady_clock::now().time_since_epoch().count());
	int n = 13;
	vector<vector<char>> a(n, vector<char>(n));
	vector<char> ab(26);
	iota(ab.begin(), ab.end(), 'a');
	set<string> snow;
	auto dfs = [&] (auto self, int x, int y) -> void {
		if (x >= n) {
			assert(checker(n, a));
			cout << n << '\n';
			for (int i = 0; i < n; ++i, putchar('\n'))
				for (int j = 0; j < n; ++j)
					putchar(a[i][j]);
			exit(0);
		}
		if (y >= n) {
			self(self, x + 1, 0);
			return;
		}
		shuffle(ab.begin(), ab.end(), eng);
		for (char v: ab) {
			vector<string> nstr;
			unordered_set<string> nstr_set;
			a[x][y] = v;
			{
				string cur(1, a[x][y]);
				for (int i = x - 1; i >= 0; --i) {
					cur += a[i][y];
					nstr.push_back(cur);
					nstr_set.insert(cur);
				}
			}
			{
				string cur(1, a[x][y]);
				for (int i = y - 1; i >= 0; --i) {
					cur += a[x][i];
					nstr.push_back(cur);
					nstr_set.insert(cur);
				}
			}
			if (nstr_set.size() != nstr.size()) continue;
			bool flag = 0;
			for (string str: nstr)
				if (snow.count(str)) {
					flag = 1;
					break;
				}
			if (flag) continue;
			for (string str: nstr)
				snow.insert(str);
			self(self, x, y + 1);
			for (string str: nstr)
				snow.erase(str);
		}
	};
	dfs(dfs, 0, 0);
	return 0;
}