import java.io.BufferedReader;
import java.io.*;
import java.util.*;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Collections;
import java.util.Arrays;

public class Main {
	public static void main(final String[] args){
    
    Scanner sc = new Scanner(System.in);
    
    String s = sc.next();
    String t = sc.next();
    int count = 0;

    //List<Character> list1 = new ArrayList<>();
    //List<Character> list2 = new ArrayList<>();

    for(int i = 0; i < s.length(); i++){
        if(s.charAt(i)==t.charAt(i)){

        }else{
            count++;
        }
    }

    //System.out.println(list1);
    //System.out.println(list2);


    //for(int i = 0; i < list1.size(); i++){
        //if(list1.get(i).equals(list2.get(i))){
        //}else{
           // count++;
        //}
    //}

    System.out.println(count);

    
    

    


    
    


    


    
    


    
	}
} import java.io.BufferedReader; BufferedReader java.io import java.io.*; io.* java import java.util.*; util.* java import java.util.ArrayList; ArrayList java.util import java.util.Iterator; Iterator java.util import java.util.List; List java.util import java.util.Collections; Collections java.util import java.util.Arrays; Arrays java.util public class Main {
	public static void main(final String[] args){
    
    Scanner sc = new Scanner(System.in);
    
    String s = sc.next();
    String t = sc.next();
    int count = 0;

    //List<Character> list1 = new ArrayList<>();
    //List<Character> list2 = new ArrayList<>();

    for(int i = 0; i < s.length(); i++){
        if(s.charAt(i)==t.charAt(i)){

        }else{
            count++;
        }
    }

    //System.out.println(list1);
    //System.out.println(list2);


    //for(int i = 0; i < list1.size(); i++){
        //if(list1.get(i).equals(list2.get(i))){
        //}else{
           // count++;
        //}
    //}

    System.out.println(count);

    
    

    


    
    


    


    
    


    
	}
} Main public static void main(final String[] args){
    
    Scanner sc = new Scanner(System.in);
    
    String s = sc.next();
    String t = sc.next();
    int count = 0;

    //List<Character> list1 = new ArrayList<>();
    //List<Character> list2 = new ArrayList<>();

    for(int i = 0; i < s.length(); i++){
        if(s.charAt(i)==t.charAt(i)){

        }else{
            count++;
        }
    }

    //System.out.println(list1);
    //System.out.println(list2);


    //for(int i = 0; i < list1.size(); i++){
        //if(list1.get(i).equals(list2.get(i))){
        //}else{
           // count++;
        //}
    //}

    System.out.println(count);

    
    

    


    
    


    


    
    


    
	} main {
    
    Scanner sc = new Scanner(System.in);
    
    String s = sc.next();
    String t = sc.next();
    int count = 0;

    //List<Character> list1 = new ArrayList<>();
    //List<Character> list2 = new ArrayList<>();

    for(int i = 0; i < s.length(); i++){
        if(s.charAt(i)==t.charAt(i)){

        }else{
            count++;
        }
    }

    //System.out.println(list1);
    //System.out.println(list2);


    //for(int i = 0; i < list1.size(); i++){
        //if(list1.get(i).equals(list2.get(i))){
        //}else{
           // count++;
        //}
    //}

    System.out.println(count);

    
    

    


    
    


    


    
    


    
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String s = sc.next(); s sc.next() sc.next sc String t = sc.next(); t sc.next() sc.next sc int count = 0; count 0 for(int i = 0; i < s.length(); i++){
        if(s.charAt(i)==t.charAt(i)){

        }else{
            count++;
        }
    } int i = 0; int i = 0; i 0 i < s.length() i s.length() s.length s i++ i++ i {
        if(s.charAt(i)==t.charAt(i)){

        }else{
            count++;
        }
    } {
        if(s.charAt(i)==t.charAt(i)){

        }else{
            count++;
        }
    } if(s.charAt(i)==t.charAt(i)){

        }else{
            count++;
        } s.charAt(i)==t.charAt(i) s.charAt(i) s.charAt s i t.charAt(i) t.charAt t i {

        } {
            count++;
        } count++ count System.out.println(count) System.out.println System.out System System.out count final String[] args args public class Main {
	public static void main(final String[] args){
    
    Scanner sc = new Scanner(System.in);
    
    String s = sc.next();
    String t = sc.next();
    int count = 0;

    //List<Character> list1 = new ArrayList<>();
    //List<Character> list2 = new ArrayList<>();

    for(int i = 0; i < s.length(); i++){
        if(s.charAt(i)==t.charAt(i)){

        }else{
            count++;
        }
    }

    //System.out.println(list1);
    //System.out.println(list2);


    //for(int i = 0; i < list1.size(); i++){
        //if(list1.get(i).equals(list2.get(i))){
        //}else{
           // count++;
        //}
    //}

    System.out.println(count);

    
    

    


    
    


    


    
    


    
	}
} public class Main {
	public static void main(final String[] args){
    
    Scanner sc = new Scanner(System.in);
    
    String s = sc.next();
    String t = sc.next();
    int count = 0;

    //List<Character> list1 = new ArrayList<>();
    //List<Character> list2 = new ArrayList<>();

    for(int i = 0; i < s.length(); i++){
        if(s.charAt(i)==t.charAt(i)){

        }else{
            count++;
        }
    }

    //System.out.println(list1);
    //System.out.println(list2);


    //for(int i = 0; i < list1.size(); i++){
        //if(list1.get(i).equals(list2.get(i))){
        //}else{
           // count++;
        //}
    //}

    System.out.println(count);

    
    

    


    
    


    


    
    


    
	}
} Main
import java.io.BufferedReader;
import java.io.*;
import java.util.*;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Collections;
import java.util.Arrays;

public class Main {
	public static void main(final String[] args){
    
    Scanner sc = new Scanner(System.in);
    
    String s = sc.next();
    String t = sc.next();
    int count = 0;

    //List<Character> list1 = new ArrayList<>();
    //List<Character> list2 = new ArrayList<>();

    for(int i = 0; i < s.length(); i++){
        if(s.charAt(i)==t.charAt(i)){

        }else{
            count++;
        }
    }

    //System.out.println(list1);
    //System.out.println(list2);


    //for(int i = 0; i < list1.size(); i++){
        //if(list1.get(i).equals(list2.get(i))){
        //}else{
           // count++;
        //}
    //}

    System.out.println(count);

    
    

    


    
    


    


    
    


    
	}
}