import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String tmpS = scanner.next();
        String S[] = tmpS.split("");
        String tmpT = scanner.next();
        String T[] = tmpT.split("");
        int count = 0;

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

        scanner.close();
        for (int i = 0; i < tmpS.length(); i++){
            if (!(S[i].equals(T[i]))){
                count++;
            }
        }
        
        System.out.println(count);
    }
} Main public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String tmpS = scanner.next();
        String S[] = tmpS.split("");
        String tmpT = scanner.next();
        String T[] = tmpT.split("");
        int count = 0;

        scanner.close();
        for (int i = 0; i < tmpS.length(); i++){
            if (!(S[i].equals(T[i]))){
                count++;
            }
        }
        
        System.out.println(count);
    } main {
        Scanner scanner = new Scanner(System.in);
        String tmpS = scanner.next();
        String S[] = tmpS.split("");
        String tmpT = scanner.next();
        String T[] = tmpT.split("");
        int count = 0;

        scanner.close();
        for (int i = 0; i < tmpS.length(); i++){
            if (!(S[i].equals(T[i]))){
                count++;
            }
        }
        
        System.out.println(count);
    } Scanner scanner = new Scanner(System.in); scanner new Scanner(System.in) String tmpS = scanner.next(); tmpS scanner.next() scanner.next scanner String S[] = tmpS.split(""); S tmpS.split("") tmpS.split tmpS "" String tmpT = scanner.next(); tmpT scanner.next() scanner.next scanner String T[] = tmpT.split(""); T tmpT.split("") tmpT.split tmpT "" int count = 0; count 0 scanner.close() scanner.close scanner for (int i = 0; i < tmpS.length(); i++){
            if (!(S[i].equals(T[i]))){
                count++;
            }
        } int i = 0; int i = 0; i 0 i < tmpS.length() i tmpS.length() tmpS.length tmpS i++ i++ i {
            if (!(S[i].equals(T[i]))){
                count++;
            }
        } {
            if (!(S[i].equals(T[i]))){
                count++;
            }
        } if (!(S[i].equals(T[i]))){
                count++;
            } !(S[i].equals(T[i])) (S[i].equals(T[i])) S[i].equals S[i] S i T[i] 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) {
        Scanner scanner = new Scanner(System.in);
        String tmpS = scanner.next();
        String S[] = tmpS.split("");
        String tmpT = scanner.next();
        String T[] = tmpT.split("");
        int count = 0;

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

        scanner.close();
        for (int i = 0; i < tmpS.length(); i++){
            if (!(S[i].equals(T[i]))){
                count++;
            }
        }
        
        System.out.println(count);
    }
} Main
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String tmpS = scanner.next();
        String S[] = tmpS.split("");
        String tmpT = scanner.next();
        String T[] = tmpT.split("");
        int count = 0;

        scanner.close();
        for (int i = 0; i < tmpS.length(); i++){
            if (!(S[i].equals(T[i]))){
                count++;
            }
        }
        
        System.out.println(count);
    }
}
