import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        
        Scanner scanner = new Scanner(System.in);
        
        String S = scanner.next();
        String T = scanner.next();
        int count = 0;
        
        for(int i=0; i<S.length(); i++){
            if(S.charAt(i)!=T.charAt(i)){
                count++;
            }
        }
        
        System.out.println(count);
    }
} import java.util.*; util.* java public class Main {
    public static void main(String[] args) throws Exception {
        
        Scanner scanner = new Scanner(System.in);
        
        String S = scanner.next();
        String T = scanner.next();
        int count = 0;
        
        for(int i=0; i<S.length(); i++){
            if(S.charAt(i)!=T.charAt(i)){
                count++;
            }
        }
        
        System.out.println(count);
    }
} Main public static void main(String[] args) throws Exception {
        
        Scanner scanner = new Scanner(System.in);
        
        String S = scanner.next();
        String T = scanner.next();
        int count = 0;
        
        for(int i=0; i<S.length(); i++){
            if(S.charAt(i)!=T.charAt(i)){
                count++;
            }
        }
        
        System.out.println(count);
    } main {
        
        Scanner scanner = new Scanner(System.in);
        
        String S = scanner.next();
        String T = scanner.next();
        int count = 0;
        
        for(int i=0; i<S.length(); i++){
            if(S.charAt(i)!=T.charAt(i)){
                count++;
            }
        }
        
        System.out.println(count);
    } Scanner scanner = new Scanner(System.in); scanner new Scanner(System.in) String S = scanner.next(); S scanner.next() scanner.next scanner String T = scanner.next(); T scanner.next() scanner.next scanner int count = 0; count 0 for(int i=0; i<S.length(); i++){
            if(S.charAt(i)!=T.charAt(i)){
                count++;
            }
        } int i=0; int i=0; i 0 i<S.length() i S.length() S.length S i++ i++ i {
            if(S.charAt(i)!=T.charAt(i)){
                count++;
            }
        } {
            if(S.charAt(i)!=T.charAt(i)){
                count++;
            }
        } if(S.charAt(i)!=T.charAt(i)){
                count++;
            } S.charAt(i)!=T.charAt(i) S.charAt(i) S.charAt S i T.charAt(i) T.charAt T 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 {
        
        Scanner scanner = new Scanner(System.in);
        
        String S = scanner.next();
        String T = scanner.next();
        int count = 0;
        
        for(int i=0; i<S.length(); i++){
            if(S.charAt(i)!=T.charAt(i)){
                count++;
            }
        }
        
        System.out.println(count);
    }
} public class Main {
    public static void main(String[] args) throws Exception {
        
        Scanner scanner = new Scanner(System.in);
        
        String S = scanner.next();
        String T = scanner.next();
        int count = 0;
        
        for(int i=0; i<S.length(); i++){
            if(S.charAt(i)!=T.charAt(i)){
                count++;
            }
        }
        
        System.out.println(count);
    }
} Main
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        
        Scanner scanner = new Scanner(System.in);
        
        String S = scanner.next();
        String T = scanner.next();
        int count = 0;
        
        for(int i=0; i<S.length(); i++){
            if(S.charAt(i)!=T.charAt(i)){
                count++;
            }
        }
        
        System.out.println(count);
    }
}
