private static void subStringGenerator(Index index, Letter root) {
index.value = root.ch;
for (Letter successor : root.children) {
if (successor != null) {
Index subIndex = index.getElementOrCreate(successor.ch);
long subSize = subIndex.size;
subStringGenerator(subIndex, successor);
index.size += subIndex.size - subSize;
}
}
}
public static void main(String[] args) throws IOException {
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
PrintWriter printWriter = new PrintWriter(System.out);
// reading dimensions
StringTokenizer stk = new StringTokenizer(bufferedReader.readLine());
int N = Integer.parseInt(stk.nextToken()), Q = Integer.parseInt(stk.nextToken());
// reading given tree
// and building the index
char alphabet[] = new char[N];
Letter letters[] = new Letter[N];
bufferedReader.read(alphabet, 0, N);
for (int i = 0; i < N; i++) {
letters[i] = new Letter(alphabet[i]);
}
bufferedReader.readLine();
for (int i = 0; i < N - 1; i++) {
stk = new StringTokenizer(bufferedReader.readLine());
Letter parent = letters[Integer.parseInt(stk.nextToken()) - 1];
int j = Integer.parseInt(stk.nextToken());
Letter child = letters[j - 1];
// uniting duplicate children by the way
if (parent.children[child.ch - 97] == null) {
parent.children[child.ch - 97] = child;
} else {
letters[j - 1] = parent.children[child.ch - 97];
}
}
// return value for K=1
index.value = ' ';
// generate all possible sub-strings
for (int i = 0; i < N - 1; i++) {
Letter letter = letters[i];
if (!letter.visited) {
letter.visited = true;
Index subIndex = index.getElementOrCreate(letter.ch);
long subSize = subIndex.size;
subStringGenerator(subIndex, letter);
index.size += subIndex.size - subSize;
}
}
// printing total number of distinct substrings
printWriter.println(index.size);
// printing answers string by string
char[] order = new char[26];
for (int i = 0; i < Q; i++) {
bufferedReader.read(order, 0, 26);
int K = Integer.parseInt(bufferedReader.readLine().substring(1));
if (K > index.size) {
printWriter.println("-1");
continue;
}
String stepAnswer = getString(index, order, K);
printWriter.println(stepAnswer);
}
printWriter.flush();
}
