Envío 5818

Código

import java.io.*;
import java.util.StringTokenizer;

class Main
{
    public static void main(String[] args) throws IOException{
        BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st;
        st = new StringTokenizer(bf.readLine());
        
        StringBuilder sb = new StringBuilder();
        sb.append(st.nextToken().toString());
        sb.reverse();
        st = new StringTokenizer(bf.readLine());
        int k = Integer.parseInt(st.nextToken());
        int x = 0;
        int clave = 0;
        
        while(x<sb.length()){
            int digito = Integer.parseInt(sb.substring(x,x+1));
            if(digito+k>9 && k>0){
                String valor = Integer.toString(digito+k);
                sb.replace(x,x+1,valor.substring(1,2));
                clave=1;
                k=0;
                x++;
                continue;
            }   
            if(clave==1){
                if(digito<9){
                    sb.replace(x,x+1,Integer.toString(digito+1));  
                    break;
                }else{
                    sb.replace(x,x+1,"0");
                }
            }
            if(digito==0){
                sb.replace(x,x+1,Integer.toString(digito+k));
                clave=5;
                break;
            }
            if(digito+k<9){
                sb.replace(x,x+1,Integer.toString(digito+k));
                break;
            }
            x++;
        }
        
        int p = 0;
        sb.reverse();
        for(int i=0;i<sb.length();i++){
            if(sb.substring(i,i+1).equals("0")){
                p++;
            }
        }
        
        if(clave==5){
            System.out.print(sb);
        }else if(p==sb.length()-1 && sb.substring(0,1).equals("0") || p==sb.length() && sb.substring(0,1).equals("0")){
            System.out.print("1"+sb);
        }else{
            System.out.println(sb);   
        }
    
    }
}