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

#define FOR(i, a, b) for(int i = (a); i < (b); i++)
#define RFOR(i, a, b) for(int i = (a) - 1; i >= (b); i--)
#define SZ(a) int(a.size())
#define ALL(a) a.begin(), a.end()
#define RALL(a) a.rbegin(), a.rend()
#define PB push_back
#define MP make_pair
#define F first
#define S second

typedef long long ll;
typedef double db;
typedef vector<int> vi;
typedef vector<long long> vll;
typedef vector<double> vd;
typedef pair<int, int> pii;
typedef pair<long long, long long> pll;
typedef vector<pair<int, int>> vpii;
typedef vector<pair<long long, long long>> vpll;
typedef set<int> si;
typedef set<long long> sll;
typedef map<int, int> mii;
typedef map<long long, long long> mll;

constexpr int INF = 1e9 + 47;
constexpr long long LINF = (ll)1e18 + 4747;
constexpr int MOD = 998244353;
constexpr int N = 1e6 + 47;

pii getVars(int l, int w, int sq)
{
	FOR (i, 1, sq + 1)
	{
		int j = sq;
		while (j > 0 && i * j != sq)
			j--;

		if (j == 0)
			continue;
		if (l % i == 0 && w % j == 0 && l / i * w / j == l * w / sq)
		{
			return MP(i, j);
		}
	}
	return MP(0, 0);
}

int main()
{
    ios_base::sync_with_stdio(false);
	cin.tie(nullptr);

	int l, w, n;
	cin >> l >> w >> n;
	if (l * w % n != 0)
	{
		cout << "impossible\n";
		return 0;
	}

	pii var = getVars(l, w, l * w / n);
	if (var.F == 0 || var.S == 0)
		cerr << "Watafak\n";

	string el;
	el.resize(w);
	vector res(l, el);
	pii start = MP(0, 0);
	char ch = 'A';
	FOR (i, 0, n)
	{
		FOR (r, start.F, start.F + var.F)
		{
			FOR (c, start.S, start.S + var.S)
			{
				res[r][c] = ch;
			}
		}
		ch++;
		start.S += var.S;
		if (start.S == w)
		{
			start.F += var.F;
			start.S = 0;
		}
	}

	FOR(i, 0, l)
		cout << res[i] << '\n';

    return 0;
}