import java.util.Scanner;

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

        String S = scan.nextLine();
        String T = scan.nextLine();

        int len = S.length();
        int ans = 0;

        for(int i = 0; i < len; i++){
            char charS = S.charAt(i);
            char charT = T.charAt(i);
            if(charS != charT){
                ans++;
            }
        }
        System.out.println(ans);
        scan.close();
    }
} import java.util.Scanner; Scanner java.util public class Main {
    public static void main(String[] args) {
        
        Scanner scan = new Scanner(System.in);

        String S = scan.nextLine();
        String T = scan.nextLine();

        int len = S.length();
        int ans = 0;

        for(int i = 0; i < len; i++){
            char charS = S.charAt(i);
            char charT = T.charAt(i);
            if(charS != charT){
                ans++;
            }
        }
        System.out.println(ans);
        scan.close();
    }
} Main public static void main(String[] args) {
        
        Scanner scan = new Scanner(System.in);

        String S = scan.nextLine();
        String T = scan.nextLine();

        int len = S.length();
        int ans = 0;

        for(int i = 0; i < len; i++){
            char charS = S.charAt(i);
            char charT = T.charAt(i);
            if(charS != charT){
                ans++;
            }
        }
        System.out.println(ans);
        scan.close();
    } main {
        
        Scanner scan = new Scanner(System.in);

        String S = scan.nextLine();
        String T = scan.nextLine();

        int len = S.length();
        int ans = 0;

        for(int i = 0; i < len; i++){
            char charS = S.charAt(i);
            char charT = T.charAt(i);
            if(charS != charT){
                ans++;
            }
        }
        System.out.println(ans);
        scan.close();
    } Scanner scan = new Scanner(System.in); scan new Scanner(System.in) String S = scan.nextLine(); S scan.nextLine() scan.nextLine scan String T = scan.nextLine(); T scan.nextLine() scan.nextLine scan int len = S.length(); len S.length() S.length S int ans = 0; ans 0 for(int i = 0; i < len; i++){
            char charS = S.charAt(i);
            char charT = T.charAt(i);
            if(charS != charT){
                ans++;
            }
        } int i = 0; int i = 0; i 0 i < len i len i++ i++ i {
            char charS = S.charAt(i);
            char charT = T.charAt(i);
            if(charS != charT){
                ans++;
            }
        } {
            char charS = S.charAt(i);
            char charT = T.charAt(i);
            if(charS != charT){
                ans++;
            }
        } char charS = S.charAt(i); charS S.charAt(i) S.charAt S i char charT = T.charAt(i); charT T.charAt(i) T.charAt T i if(charS != charT){
                ans++;
            } charS != charT charS charT {
                ans++;
            } ans++ ans System.out.println(ans) System.out.println System.out System System.out ans scan.close() scan.close scan String[] args args public class Main {
    public static void main(String[] args) {
        
        Scanner scan = new Scanner(System.in);

        String S = scan.nextLine();
        String T = scan.nextLine();

        int len = S.length();
        int ans = 0;

        for(int i = 0; i < len; i++){
            char charS = S.charAt(i);
            char charT = T.charAt(i);
            if(charS != charT){
                ans++;
            }
        }
        System.out.println(ans);
        scan.close();
    }
} public class Main {
    public static void main(String[] args) {
        
        Scanner scan = new Scanner(System.in);

        String S = scan.nextLine();
        String T = scan.nextLine();

        int len = S.length();
        int ans = 0;

        for(int i = 0; i < len; i++){
            char charS = S.charAt(i);
            char charT = T.charAt(i);
            if(charS != charT){
                ans++;
            }
        }
        System.out.println(ans);
        scan.close();
    }
} Main
import java.util.Scanner;

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

        String S = scan.nextLine();
        String T = scan.nextLine();

        int len = S.length();
        int ans = 0;

        for(int i = 0; i < len; i++){
            char charS = S.charAt(i);
            char charT = T.charAt(i);
            if(charS != charT){
                ans++;
            }
        }
        System.out.println(ans);
        scan.close();
    }
}
