import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        int sum = 0;
        String S = sc.next();
        String T = sc.next();
        String s[] = S.split("");
        String t[] = T.split("");
        for(int i=0;i<s.length;i++){
            if(!s[i].equals(t[i])){
                sum++;
            }
        }
        System.out.println(sum);
    }
} import java.util.*; util.* java public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        int sum = 0;
        String S = sc.next();
        String T = sc.next();
        String s[] = S.split("");
        String t[] = T.split("");
        for(int i=0;i<s.length;i++){
            if(!s[i].equals(t[i])){
                sum++;
            }
        }
        System.out.println(sum);
    }
} Main public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        int sum = 0;
        String S = sc.next();
        String T = sc.next();
        String s[] = S.split("");
        String t[] = T.split("");
        for(int i=0;i<s.length;i++){
            if(!s[i].equals(t[i])){
                sum++;
            }
        }
        System.out.println(sum);
    } main {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        int sum = 0;
        String S = sc.next();
        String T = sc.next();
        String s[] = S.split("");
        String t[] = T.split("");
        for(int i=0;i<s.length;i++){
            if(!s[i].equals(t[i])){
                sum++;
            }
        }
        System.out.println(sum);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int sum = 0; sum 0 String S = sc.next(); S sc.next() sc.next sc String T = sc.next(); T sc.next() sc.next sc String s[] = S.split(""); s S.split("") S.split S "" String t[] = T.split(""); t T.split("") T.split T "" for(int i=0;i<s.length;i++){
            if(!s[i].equals(t[i])){
                sum++;
            }
        } int i=0; int i=0; i 0 i<s.length i s.length s s.length i++ i++ i {
            if(!s[i].equals(t[i])){
                sum++;
            }
        } {
            if(!s[i].equals(t[i])){
                sum++;
            }
        } if(!s[i].equals(t[i])){
                sum++;
            } !s[i].equals(t[i]) s[i].equals(t[i]) s[i].equals s[i] s i t[i] t i {
                sum++;
            } sum++ sum System.out.println(sum) System.out.println System.out System System.out sum String[] args args public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        int sum = 0;
        String S = sc.next();
        String T = sc.next();
        String s[] = S.split("");
        String t[] = T.split("");
        for(int i=0;i<s.length;i++){
            if(!s[i].equals(t[i])){
                sum++;
            }
        }
        System.out.println(sum);
    }
} public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        int sum = 0;
        String S = sc.next();
        String T = sc.next();
        String s[] = S.split("");
        String t[] = T.split("");
        for(int i=0;i<s.length;i++){
            if(!s[i].equals(t[i])){
                sum++;
            }
        }
        System.out.println(sum);
    }
} Main
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        int sum = 0;
        String S = sc.next();
        String T = sc.next();
        String s[] = S.split("");
        String t[] = T.split("");
        for(int i=0;i<s.length;i++){
            if(!s[i].equals(t[i])){
                sum++;
            }
        }
        System.out.println(sum);
    }
}