import java.util.*;
public class Main {

    public static void main(String[] args) throws Exception {
        Scanner sc = null;
        sc = new Scanner(System.in);
        String s = sc.nextLine();	
        String t = sc.nextLine();
        sc.close();	
        char[] cs = s.toCharArray();
        char[] ct = t.toCharArray();
        int count = 0;
        for (int i = 0; i < cs.length; i++) {
            if (cs[i] != ct[i]) {
                count +=1;
            } 
        }
        System.out.println(count);   
    }
    
} import java.util.*; util.* java public class Main {

    public static void main(String[] args) throws Exception {
        Scanner sc = null;
        sc = new Scanner(System.in);
        String s = sc.nextLine();	
        String t = sc.nextLine();
        sc.close();	
        char[] cs = s.toCharArray();
        char[] ct = t.toCharArray();
        int count = 0;
        for (int i = 0; i < cs.length; i++) {
            if (cs[i] != ct[i]) {
                count +=1;
            } 
        }
        System.out.println(count);   
    }
    
} Main public static void main(String[] args) throws Exception {
        Scanner sc = null;
        sc = new Scanner(System.in);
        String s = sc.nextLine();	
        String t = sc.nextLine();
        sc.close();	
        char[] cs = s.toCharArray();
        char[] ct = t.toCharArray();
        int count = 0;
        for (int i = 0; i < cs.length; i++) {
            if (cs[i] != ct[i]) {
                count +=1;
            } 
        }
        System.out.println(count);   
    } main {
        Scanner sc = null;
        sc = new Scanner(System.in);
        String s = sc.nextLine();	
        String t = sc.nextLine();
        sc.close();	
        char[] cs = s.toCharArray();
        char[] ct = t.toCharArray();
        int count = 0;
        for (int i = 0; i < cs.length; i++) {
            if (cs[i] != ct[i]) {
                count +=1;
            } 
        }
        System.out.println(count);   
    } Scanner sc = null; sc null sc = new Scanner(System.in) sc new Scanner(System.in) String s = sc.nextLine(); s sc.nextLine() sc.nextLine sc String t = sc.nextLine(); t sc.nextLine() sc.nextLine sc sc.close() sc.close sc char[] cs = s.toCharArray(); cs s.toCharArray() s.toCharArray s char[] ct = t.toCharArray(); ct t.toCharArray() t.toCharArray t int count = 0; count 0 for (int i = 0; i < cs.length; i++) {
            if (cs[i] != ct[i]) {
                count +=1;
            } 
        } int i = 0; int i = 0; i 0 i < cs.length i cs.length cs cs.length i++ i++ i {
            if (cs[i] != ct[i]) {
                count +=1;
            } 
        } {
            if (cs[i] != ct[i]) {
                count +=1;
            } 
        } if (cs[i] != ct[i]) {
                count +=1;
            } cs[i] != ct[i] cs[i] cs i ct[i] ct i {
                count +=1;
            } count +=1 count 1 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 = null;
        sc = new Scanner(System.in);
        String s = sc.nextLine();	
        String t = sc.nextLine();
        sc.close();	
        char[] cs = s.toCharArray();
        char[] ct = t.toCharArray();
        int count = 0;
        for (int i = 0; i < cs.length; i++) {
            if (cs[i] != ct[i]) {
                count +=1;
            } 
        }
        System.out.println(count);   
    }
    
} public class Main {

    public static void main(String[] args) throws Exception {
        Scanner sc = null;
        sc = new Scanner(System.in);
        String s = sc.nextLine();	
        String t = sc.nextLine();
        sc.close();	
        char[] cs = s.toCharArray();
        char[] ct = t.toCharArray();
        int count = 0;
        for (int i = 0; i < cs.length; i++) {
            if (cs[i] != ct[i]) {
                count +=1;
            } 
        }
        System.out.println(count);   
    }
    
} Main
import java.util.*;
public class Main {

    public static void main(String[] args) throws Exception {
        Scanner sc = null;
        sc = new Scanner(System.in);
        String s = sc.nextLine();	
        String t = sc.nextLine();
        sc.close();	
        char[] cs = s.toCharArray();
        char[] ct = t.toCharArray();
        int count = 0;
        for (int i = 0; i < cs.length; i++) {
            if (cs[i] != ct[i]) {
                count +=1;
            } 
        }
        System.out.println(count);   
    }
    
}