// editor3
#include<stdio.h>
#include<string.h>
#include<ctype.h>
#define MAX_LENGTH 101
void highlight_vowels(char *s){
    if (s == NULL){
        return;
    }
    int i = 0;
    while (s[i] != '\0'){
        char ch = s[i];
        if (!isalpha(ch) && ch != ' '){
            printf("Invalid input\n");
            return ;
        }
        if (ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u'){
        s[i] = toupper(ch);
    }
    i++;
}
printf("%s\n", s);
}
int main(){
    char str1[MAX_LENGTH];
    char str2[MAX_LENGTH];
    strcpy(str1, "A librarian is organizing a collection of books");
    higlight_vowels(str1);
    strcpy(str2, "hello 123 world");
    highlight_vowels(str2);
    return 0;
}