import java.util.Scanner;

public class Main{
    public static void main (String[] args){
        Scanner scanner = new Scanner(System.in);
        String  s = scanner.nextLine();
        String t = scanner.nextLine();

        char[] s_a = s.toCharArray();
        char[] t_a = t.toCharArray();

        int count = 0;

        for(int i = 0; i <= s_a.length -1; i++ ){
            if(!(s_a[i] == t_a[i])){
                count +=1;
            }
        }
        System.out.println(count);
    }
} import java.util.Scanner; Scanner java.util public class Main{
    public static void main (String[] args){
        Scanner scanner = new Scanner(System.in);
        String  s = scanner.nextLine();
        String t = scanner.nextLine();

        char[] s_a = s.toCharArray();
        char[] t_a = t.toCharArray();

        int count = 0;

        for(int i = 0; i <= s_a.length -1; i++ ){
            if(!(s_a[i] == t_a[i])){
                count +=1;
            }
        }
        System.out.println(count);
    }
} Main public static void main (String[] args){
        Scanner scanner = new Scanner(System.in);
        String  s = scanner.nextLine();
        String t = scanner.nextLine();

        char[] s_a = s.toCharArray();
        char[] t_a = t.toCharArray();

        int count = 0;

        for(int i = 0; i <= s_a.length -1; i++ ){
            if(!(s_a[i] == t_a[i])){
                count +=1;
            }
        }
        System.out.println(count);
    } main {
        Scanner scanner = new Scanner(System.in);
        String  s = scanner.nextLine();
        String t = scanner.nextLine();

        char[] s_a = s.toCharArray();
        char[] t_a = t.toCharArray();

        int count = 0;

        for(int i = 0; i <= s_a.length -1; i++ ){
            if(!(s_a[i] == t_a[i])){
                count +=1;
            }
        }
        System.out.println(count);
    } Scanner scanner = new Scanner(System.in); scanner new Scanner(System.in) String  s = scanner.nextLine(); s scanner.nextLine() scanner.nextLine scanner String t = scanner.nextLine(); t scanner.nextLine() scanner.nextLine scanner char[] s_a = s.toCharArray(); s_a s.toCharArray() s.toCharArray s char[] t_a = t.toCharArray(); t_a t.toCharArray() t.toCharArray t int count = 0; count 0 for(int i = 0; i <= s_a.length -1; i++ ){
            if(!(s_a[i] == t_a[i])){
                count +=1;
            }
        } int i = 0; int i = 0; i 0 i <= s_a.length -1 i s_a.length -1 s_a.length s_a s_a.length 1 i++ i++ i {
            if(!(s_a[i] == t_a[i])){
                count +=1;
            }
        } {
            if(!(s_a[i] == t_a[i])){
                count +=1;
            }
        } if(!(s_a[i] == t_a[i])){
                count +=1;
            } !(s_a[i] == t_a[i]) (s_a[i] == t_a[i]) s_a[i] s_a i t_a[i] t_a 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){
        Scanner scanner = new Scanner(System.in);
        String  s = scanner.nextLine();
        String t = scanner.nextLine();

        char[] s_a = s.toCharArray();
        char[] t_a = t.toCharArray();

        int count = 0;

        for(int i = 0; i <= s_a.length -1; i++ ){
            if(!(s_a[i] == t_a[i])){
                count +=1;
            }
        }
        System.out.println(count);
    }
} public class Main{
    public static void main (String[] args){
        Scanner scanner = new Scanner(System.in);
        String  s = scanner.nextLine();
        String t = scanner.nextLine();

        char[] s_a = s.toCharArray();
        char[] t_a = t.toCharArray();

        int count = 0;

        for(int i = 0; i <= s_a.length -1; i++ ){
            if(!(s_a[i] == t_a[i])){
                count +=1;
            }
        }
        System.out.println(count);
    }
} Main
import java.util.Scanner;

public class Main{
    public static void main (String[] args){
        Scanner scanner = new Scanner(System.in);
        String  s = scanner.nextLine();
        String t = scanner.nextLine();

        char[] s_a = s.toCharArray();
        char[] t_a = t.toCharArray();

        int count = 0;

        for(int i = 0; i <= s_a.length -1; i++ ){
            if(!(s_a[i] == t_a[i])){
                count +=1;
            }
        }
        System.out.println(count);
    }
}
