C++ :

#include <bits/stdc++.h>
using namespace std;

int main(){
	string s;
	getline(cin,s);
	for(int i = 0;i < s.size();i++){
		s[i] = tolower(s[i]);
		
		if(s[i]=='a'||s[i]=='e'||s[i]=='i'||s[i]=='o'||s[i]=='u'){
			s[i] = toupper(s[i]);
		}else{
			s[i] = tolower(s[i]);
		}
	}
	cout<<s;
	return 0;
}

Java :

import java.util.Scanner;

public class Main{
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String x = sc.nextLine();
        char c;
        String s;
        s = x.toLowerCase();
        for (int i = 0; i < s.length(); i++) {
            c = s.charAt(i);
            if (c == 97) {
                System.out.print('A');
            } else if (c == 101) {
                System.out.print('E');
            } else if (c == 105) {
                System.out.print('I');
            } else if (c == 111) {
                System.out.print('O');
            } else if (c == 117) {
                System.out.print('U');
            } else {
                System.out.print(c);
            }

        }

    }
}