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

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        String s = sc.next();
        String t = sc.next();
        int count = 0;
        for(int i = 0;i<s.length();i++){
            char ss = s.charAt(i);
            char tt = t.charAt(i);
            if(ss != tt)count++;
        }
        System.out.println(count);
    }
} import java.util.*; util.* java import java.io.*; io.* java public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        String s = sc.next();
        String t = sc.next();
        int count = 0;
        for(int i = 0;i<s.length();i++){
            char ss = s.charAt(i);
            char tt = t.charAt(i);
            if(ss != tt)count++;
        }
        System.out.println(count);
    }
} Main public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        String s = sc.next();
        String t = sc.next();
        int count = 0;
        for(int i = 0;i<s.length();i++){
            char ss = s.charAt(i);
            char tt = t.charAt(i);
            if(ss != tt)count++;
        }
        System.out.println(count);
    } main {
        Scanner sc = new Scanner(System.in);
        String s = sc.next();
        String t = sc.next();
        int count = 0;
        for(int i = 0;i<s.length();i++){
            char ss = s.charAt(i);
            char tt = t.charAt(i);
            if(ss != tt)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++){
            char ss = s.charAt(i);
            char tt = t.charAt(i);
            if(ss != tt)count++;
        } int i = 0; int i = 0; i 0 i<s.length() i s.length() s.length s i++ i++ i {
            char ss = s.charAt(i);
            char tt = t.charAt(i);
            if(ss != tt)count++;
        } {
            char ss = s.charAt(i);
            char tt = t.charAt(i);
            if(ss != tt)count++;
        } char ss = s.charAt(i); ss s.charAt(i) s.charAt s i char tt = t.charAt(i); tt t.charAt(i) t.charAt t i if(ss != tt)count++; ss != tt ss tt count++ count System.out.println(count) System.out.println System.out System System.out count String[] args args public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        String s = sc.next();
        String t = sc.next();
        int count = 0;
        for(int i = 0;i<s.length();i++){
            char ss = s.charAt(i);
            char tt = t.charAt(i);
            if(ss != tt)count++;
        }
        System.out.println(count);
    }
} public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        String s = sc.next();
        String t = sc.next();
        int count = 0;
        for(int i = 0;i<s.length();i++){
            char ss = s.charAt(i);
            char tt = t.charAt(i);
            if(ss != tt)count++;
        }
        System.out.println(count);
    }
} Main
import java.util.*;
import java.io.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        String s = sc.next();
        String t = sc.next();
        int count = 0;
        for(int i = 0;i<s.length();i++){
            char ss = s.charAt(i);
            char tt = t.charAt(i);
            if(ss != tt)count++;
        }
        System.out.println(count);
    }
}