class Solution {
public:
    vector<char> vowels = {'a', 'e', 'i', 'o', 'u'};
    int count=0,size=0;
    int countVowelStrings(int n) {
        size=n;
        getVowelStrings(n,0, "");
        return count;
    }
    
    void getVowelStrings(int n,int start, string out){
        if(n<0) return;
        if(out.size() == size) {
            count+=1;
            return;
        }
        for(int i=start;i<vowels.size();i++){
            getVowelStrings(n-1, i, out+vowels[i]);
        }
    }
};