Untitled

class Solution {
    public int countVowelStrings(int n) {
        return solve(0, n);
    }

    private int solve(int index, int remLength) {
        // Base case: If no length is remaining, we have formed a valid string
        if (remLength == 0) return 1;

        int ways = 0;

        // Iterate through all valid vowel indices starting from the current index
        for (int i = index; i < 5; i++) {
            ways += solve(i, remLength - 1);
        }

        return ways;
    }
}