import java.util.*;
import java.lang.Math;
public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String T = sc.next();
        char[] work = new char[S.length()];
        char[] work2 = new char[T.length()];
        int counter = 0;
        for(int i = 0; i < S.length(); i++){
                work[i] = S.charAt(i);
                work2[i] = T.charAt(i);
                if(work[i] != work2[i]){
                    counter++;
                }
            }
        System.out.println(counter);
    }
} import java.util.*; util.* java import java.lang.Math; Math java.lang public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String T = sc.next();
        char[] work = new char[S.length()];
        char[] work2 = new char[T.length()];
        int counter = 0;
        for(int i = 0; i < S.length(); i++){
                work[i] = S.charAt(i);
                work2[i] = T.charAt(i);
                if(work[i] != work2[i]){
                    counter++;
                }
            }
        System.out.println(counter);
    }
} Main public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String T = sc.next();
        char[] work = new char[S.length()];
        char[] work2 = new char[T.length()];
        int counter = 0;
        for(int i = 0; i < S.length(); i++){
                work[i] = S.charAt(i);
                work2[i] = T.charAt(i);
                if(work[i] != work2[i]){
                    counter++;
                }
            }
        System.out.println(counter);
    } main {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String T = sc.next();
        char[] work = new char[S.length()];
        char[] work2 = new char[T.length()];
        int counter = 0;
        for(int i = 0; i < S.length(); i++){
                work[i] = S.charAt(i);
                work2[i] = T.charAt(i);
                if(work[i] != work2[i]){
                    counter++;
                }
            }
        System.out.println(counter);
    } 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 char[] work = new char[S.length()]; work new char[S.length()] S.length() S.length S char[] work2 = new char[T.length()]; work2 new char[T.length()] T.length() T.length T int counter = 0; counter 0 for(int i = 0; i < S.length(); i++){
                work[i] = S.charAt(i);
                work2[i] = T.charAt(i);
                if(work[i] != work2[i]){
                    counter++;
                }
            } int i = 0; int i = 0; i 0 i < S.length() i S.length() S.length S i++ i++ i {
                work[i] = S.charAt(i);
                work2[i] = T.charAt(i);
                if(work[i] != work2[i]){
                    counter++;
                }
            } {
                work[i] = S.charAt(i);
                work2[i] = T.charAt(i);
                if(work[i] != work2[i]){
                    counter++;
                }
            } work[i] = S.charAt(i) work[i] work i S.charAt(i) S.charAt S i work2[i] = T.charAt(i) work2[i] work2 i T.charAt(i) T.charAt T i if(work[i] != work2[i]){
                    counter++;
                } work[i] != work2[i] work[i] work i work2[i] work2 i {
                    counter++;
                } counter++ counter System.out.println(counter) System.out.println System.out System System.out counter String[] args args public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String T = sc.next();
        char[] work = new char[S.length()];
        char[] work2 = new char[T.length()];
        int counter = 0;
        for(int i = 0; i < S.length(); i++){
                work[i] = S.charAt(i);
                work2[i] = T.charAt(i);
                if(work[i] != work2[i]){
                    counter++;
                }
            }
        System.out.println(counter);
    }
} public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String T = sc.next();
        char[] work = new char[S.length()];
        char[] work2 = new char[T.length()];
        int counter = 0;
        for(int i = 0; i < S.length(); i++){
                work[i] = S.charAt(i);
                work2[i] = T.charAt(i);
                if(work[i] != work2[i]){
                    counter++;
                }
            }
        System.out.println(counter);
    }
} Main
import java.util.*;
import java.lang.Math;
public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String T = sc.next();
        char[] work = new char[S.length()];
        char[] work2 = new char[T.length()];
        int counter = 0;
        for(int i = 0; i < S.length(); i++){
                work[i] = S.charAt(i);
                work2[i] = T.charAt(i);
                if(work[i] != work2[i]){
                    counter++;
                }
            }
        System.out.println(counter);
    }
}
