京东第一题0%怎么回事，求解答

import java.util.*;

public class Main{
    public static void main(String[] args){
    	Scanner sc = new Scanner(System.in);
    	while(sc.hasNext()){
    		String str = sc.nextLine();
    		int n = Integer.valueOf(str);
    		String a1 = sc.nextLine();
    		String a2 = sc.nextLine();
    		String re = "";
    		for(int i=0; i<n; i++){
    			char c1 = a1.charAt(i);
    			char c2 = a2.charAt(i);
    			if(c1=='0'&& c2=='1'){
    				re = re+"1";
    			}else if(c1=='1'&& c2=='0'){
    				re = re+"1";
    			}else{
    				re = re+"0";
    			}
    		}
    		System.out.println(re);
    		while(re.charAt(0)=='0'){
    			re = re.substring(1);
    		}
    		int r=0;
    		int temp=1;
    		for(int i=re.length()-1; i>=0; i--){
    			if(re.charAt(i)=='1'){
    				r += temp;
    			}
    			temp = temp*2;
    		}
    		System.out.println(r);
    	}
    }
}