오류좀 봐주셤들요 ㅜㅜ

[박박(112.187)]

import java.util.Scanner;
public class quiz_1 {

 /**
  * @param args
  */
 public static void main(String[] args) {
  Scanner scan= new Scanner(System.in);
  int menu,num1,num2;
  int con=0;
  String sel;
  do{
        System.out.println(\"메뉴를 선택하시오(1.더하기 2.빼기 3.곱하기 4.나누기)\");
        menu= scan.nextInt();
             if(menu==1){
            System.out.println(\"정수 2개를 입력하시오\");
             num1=scan.nextInt();
             num2=scan.nextInt();
             System.out.println(sum(num1,num2));
   
           }
           else if(menu==3){
            System.out.println(\"정수 2개를 입력하시오\");
            num1=scan.nextInt();
           num2=scan.nextInt();
          System.out.println(mul(num1,num2));
   
  }
  else if(menu==4){
   System.out.println(\"정수 2개를 입력하시오\");
   num1=scan.nextInt();
   num2=scan.nextInt();
   System.out.println(nanu(num1,num2));
  }
  else{
   System.out.println(\"잘못 누르셨습니다\");
   
  }
  System.out.println(\"프로그램을 시작할까요?(예(1),아니오(2))\");
  sel= in.next();
  }while(sel.toLowerCase().equals(\"y\"));
  System.out.println(\"종료하셨습니다\");
 }
 
  
  
  
  // TODO Auto-generated method stub

 

 static int sum(int a,int b){
  return a+b;
 }
 static int bbel(int a,int b){
  return a-b;
 }
 static int mul(int a,int b){
  return a*b;
 }
 static double nanu(int a, int b){
  return a/b;
 }
 
  // TODO Auto-generated method stub

 }
위에 중에 sel= in.next()요부분서 in에 오류가 나는데 원인이뭘까요