#include <stdio.h>
#include <ctype.h>

int main()
{
    printf("Enter characters: ");
    int c;
    while ((c = getchar()) != '\n') {
        if (isalpha(c)) { 
            if (c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u' ||
                c == 'A' || c == 'E' || c == 'I' || c == 'O' || c == 'U') {
                putchar(toupper(c)); 
            } else {
                putchar(tolower(c)); 
            }
        }
    }
    return 0;
}