Time + 15 Minutes

package com.company;

import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int hr = Integer.parseInt(sc.nextLine());
        int mm = Integer.parseInt(sc.nextLine());
        int clockafter15min = mm + 15;
        if (clockafter15min >= 60){
            hr++;
            clockafter15min -=60;
        }

        if (hr ==24) {
            hr -= 24;
        }

        if (clockafter15min >= 10) {
            System.out.println(+hr +":" +clockafter15min);
        } else {
            System.out.println(+hr +":0" +clockafter15min);
        }
    }
}