#include <iostream>
#include <cstdio>
#include <cctype>
#include <utility>
#include <vector>
#include <string>
#include <algorithm>
#include <set>

using namespace std;

typedef pair<int, int> PII;

set<PII> T;
vector<string> V;
int cnt, M, N, K, poc, chyba; //rieseni, rozmery, tehliciek, doteraz doplnenych, celkovo na doplnenie

void skus(int x, int y){
	//cout << x << " " << y << endl;
	if (y < N-1){
		PII pom = PII(min(V[x][y], V[x][y+1]), max(V[x][y], V[x][y+1]));
		if (T.find(pom) != T.end()){
			//cout << "vodorovna " << (char)pom.first << " " << (char)pom.second << endl;
			T.erase(pom);
			char xy = V[x][y]; V[x][y] = '[';
			char yx = V[x][y+1]; V[x][y+1] = ']';
			poc += 2;
			if (poc == chyba) { if (!cnt++) for (int i = 0; i < M; i++) cout << V[i] << endl; }
			else for (int i = 0; i < M*N; i++){
				//cout << "   " << V[i/N][i%N] << isdigit(V[i/N][i%N]) << endl;
			   	if(isdigit(V[i/N][i%N])) {
				   	skus(i/N, i%N);
				   	break;
			   	}
			}
			V[x][y] = xy;
			V[x][y+1] = yx;
			T.insert(pom);
			poc -= 2;
		}
	}
	if (x < M-1){
		PII pom = PII(min(V[x][y], V[x+1][y]), max(V[x][y], V[x+1][y]));
		if (T.find(pom) != T.end()){
			//cout << "zvisla " << (char)pom.first << " " << (char)pom.second << endl;
			T.erase(pom);
			char xy = V[x][y]; V[x][y] = 'n';
			char yx = V[x+1][y]; V[x+1][y] = 'u';
			poc += 2;
			if (poc == chyba){ if (!cnt++) for (int i = 0; i < M; i++) cout << V[i] << endl; }
			else for (int i = 0; i < M*N; i++) if(isdigit(V[i/N][i%N])) { skus(i/N, i%N); break; }
			V[x][y] = xy;
			V[x+1][y] = yx;
			T.insert(pom);
			poc -= 2;
		}
	}
}

int main(void){
	while(8){
		scanf("%d %d %d", &M, &N, &K);
		if (M == 0) break;

		V.resize(0); V.resize(M+47);
		T.clear();

		for (int i = 0; i < K; i++){
			char a, b;
			scanf(" %c %c", &a, &b);
			T.insert(PII(min(a, b), max(a, b)));
		}
		chyba = 0;
		for (int i = 0; i < M; i++){
			for (int j = 0; j < N; j++){
				char c;
				scanf(" %c", &c);
			   	V[i] += c;
				if (c != 'X') chyba++;
			}
		}
		if (!chyba)
		{
			for (int i = 0; i < M; ++i)
				cout << V[i] << endl;
			cout << 0 << endl << endl;
			continue;
		}
		//for (int i = 0; i < M; i++) cout << V[i] << endl;
		//for (set<PII>::iterator it = T.begin(); it != T.end(); it++) cout << (char)(it -> first) << " " << (char)(it -> second) << endl;
		cnt = poc = 0;
		skus(0, 0);

		if (cnt == 0) cout << "impossible" << endl << endl;
		else{
			cout << cnt-1 << endl << endl;
		}
	}
}