import java.util.*;

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[] Schar = new char[S.length()];
        char[] Tchar = new char[T.length()];
        int count = 0;
        
        
        
        for(int i=0;i<S.length();i++){
            Schar[i] = S.charAt(i);
            Tchar[i] = T.charAt(i);
            if(Schar[i]!=Tchar[i]){
                count++;
            }
        }
        
        System.out.println(count);
    }
} 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);
        String S = sc.next();
        String T = sc.next();
        
        char[] Schar = new char[S.length()];
        char[] Tchar = new char[T.length()];
        int count = 0;
        
        
        
        for(int i=0;i<S.length();i++){
            Schar[i] = S.charAt(i);
            Tchar[i] = T.charAt(i);
            if(Schar[i]!=Tchar[i]){
                count++;
            }
        }
        
        System.out.println(count);
    }
} 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[] Schar = new char[S.length()];
        char[] Tchar = new char[T.length()];
        int count = 0;
        
        
        
        for(int i=0;i<S.length();i++){
            Schar[i] = S.charAt(i);
            Tchar[i] = T.charAt(i);
            if(Schar[i]!=Tchar[i]){
                count++;
            }
        }
        
        System.out.println(count);
    } main {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String T = sc.next();
        
        char[] Schar = new char[S.length()];
        char[] Tchar = new char[T.length()];
        int count = 0;
        
        
        
        for(int i=0;i<S.length();i++){
            Schar[i] = S.charAt(i);
            Tchar[i] = T.charAt(i);
            if(Schar[i]!=Tchar[i]){
                count++;
            }
        }
        
        System.out.println(count);
    } 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[] Schar = new char[S.length()]; Schar new char[S.length()] S.length() S.length S char[] Tchar = new char[T.length()]; Tchar new char[T.length()] T.length() T.length T int count = 0; count 0 for(int i=0;i<S.length();i++){
            Schar[i] = S.charAt(i);
            Tchar[i] = T.charAt(i);
            if(Schar[i]!=Tchar[i]){
                count++;
            }
        } int i=0; int i=0; i 0 i<S.length() i S.length() S.length S i++ i++ i {
            Schar[i] = S.charAt(i);
            Tchar[i] = T.charAt(i);
            if(Schar[i]!=Tchar[i]){
                count++;
            }
        } {
            Schar[i] = S.charAt(i);
            Tchar[i] = T.charAt(i);
            if(Schar[i]!=Tchar[i]){
                count++;
            }
        } Schar[i] = S.charAt(i) Schar[i] Schar i S.charAt(i) S.charAt S i Tchar[i] = T.charAt(i) Tchar[i] Tchar i T.charAt(i) T.charAt T i if(Schar[i]!=Tchar[i]){
                count++;
            } Schar[i]!=Tchar[i] Schar[i] Schar i Tchar[i] Tchar i {
                count++;
            } count++ count 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) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String T = sc.next();
        
        char[] Schar = new char[S.length()];
        char[] Tchar = new char[T.length()];
        int count = 0;
        
        
        
        for(int i=0;i<S.length();i++){
            Schar[i] = S.charAt(i);
            Tchar[i] = T.charAt(i);
            if(Schar[i]!=Tchar[i]){
                count++;
            }
        }
        
        System.out.println(count);
    }
} 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[] Schar = new char[S.length()];
        char[] Tchar = new char[T.length()];
        int count = 0;
        
        
        
        for(int i=0;i<S.length();i++){
            Schar[i] = S.charAt(i);
            Tchar[i] = T.charAt(i);
            if(Schar[i]!=Tchar[i]){
                count++;
            }
        }
        
        System.out.println(count);
    }
} Main
import java.util.*;

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[] Schar = new char[S.length()];
        char[] Tchar = new char[T.length()];
        int count = 0;
        
        
        
        for(int i=0;i<S.length();i++){
            Schar[i] = S.charAt(i);
            Tchar[i] = T.charAt(i);
            if(Schar[i]!=Tchar[i]){
                count++;
            }
        }
        
        System.out.println(count);
    }
}
