import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        String a = sc.next();
        String b = sc.next();
        char [] aa = a.toCharArray();
        char [] bb = b.toCharArray();
        int cnt = 0;
        
        for(int i=0; i < aa.length; i++){
            if(aa[i] != bb[i]){
                cnt++;
            }
        }
        
        System.out.println(cnt);
    }
} import java.util.*; util.* java public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        String a = sc.next();
        String b = sc.next();
        char [] aa = a.toCharArray();
        char [] bb = b.toCharArray();
        int cnt = 0;
        
        for(int i=0; i < aa.length; i++){
            if(aa[i] != bb[i]){
                cnt++;
            }
        }
        
        System.out.println(cnt);
    }
} Main public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        String a = sc.next();
        String b = sc.next();
        char [] aa = a.toCharArray();
        char [] bb = b.toCharArray();
        int cnt = 0;
        
        for(int i=0; i < aa.length; i++){
            if(aa[i] != bb[i]){
                cnt++;
            }
        }
        
        System.out.println(cnt);
    } main {
        Scanner sc = new Scanner(System.in);
        String a = sc.next();
        String b = sc.next();
        char [] aa = a.toCharArray();
        char [] bb = b.toCharArray();
        int cnt = 0;
        
        for(int i=0; i < aa.length; i++){
            if(aa[i] != bb[i]){
                cnt++;
            }
        }
        
        System.out.println(cnt);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String a = sc.next(); a sc.next() sc.next sc String b = sc.next(); b sc.next() sc.next sc char [] aa = a.toCharArray(); aa a.toCharArray() a.toCharArray a char [] bb = b.toCharArray(); bb b.toCharArray() b.toCharArray b int cnt = 0; cnt 0 for(int i=0; i < aa.length; i++){
            if(aa[i] != bb[i]){
                cnt++;
            }
        } int i=0; int i=0; i 0 i < aa.length i aa.length aa aa.length i++ i++ i {
            if(aa[i] != bb[i]){
                cnt++;
            }
        } {
            if(aa[i] != bb[i]){
                cnt++;
            }
        } if(aa[i] != bb[i]){
                cnt++;
            } aa[i] != bb[i] aa[i] aa i bb[i] bb i {
                cnt++;
            } cnt++ cnt System.out.println(cnt) System.out.println System.out System System.out cnt String[] args args public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        String a = sc.next();
        String b = sc.next();
        char [] aa = a.toCharArray();
        char [] bb = b.toCharArray();
        int cnt = 0;
        
        for(int i=0; i < aa.length; i++){
            if(aa[i] != bb[i]){
                cnt++;
            }
        }
        
        System.out.println(cnt);
    }
} public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        String a = sc.next();
        String b = sc.next();
        char [] aa = a.toCharArray();
        char [] bb = b.toCharArray();
        int cnt = 0;
        
        for(int i=0; i < aa.length; i++){
            if(aa[i] != bb[i]){
                cnt++;
            }
        }
        
        System.out.println(cnt);
    }
} Main
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        String a = sc.next();
        String b = sc.next();
        char [] aa = a.toCharArray();
        char [] bb = b.toCharArray();
        int cnt = 0;
        
        for(int i=0; i < aa.length; i++){
            if(aa[i] != bb[i]){
                cnt++;
            }
        }
        
        System.out.println(cnt);
    }
}
