String obsession

import java.util.*;

public class Main {
    
    private static int maxRemovals(String currentString, List<String> substrings, Map<String, Integer> memo) {
        if (memo.containsKey(currentString)) {
            return memo.get(currentString);
        }

        int maxCount = 0;

        for (String substring : substrings) {
            int position = currentString.indexOf(substring);
            if (position != -1) {
                String newString = currentString.substring(0, position) + currentString.substring(position + substring.length());
                maxCount = Math.max(maxCount, 1 + maxRemovals(newString, substrings, memo));
            }
        }

        memo.put(currentString, maxCount);
        return maxCount;
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int numSubstrings = sc.nextInt();
        List<String> substrings = new ArrayList<>();

        for (int i = 0; i < numSubstrings; i++) {
            substrings.add(sc.next());
        }

        String mainString = sc.next();
        Map<String, Integer> memo = new HashMap<>();

        System.out.println(maxRemovals(mainString, substrings, memo));
    }
}