import java.util.Scanner;

public class Main {
    static Scanner sc = new Scanner(System.in);
    public static void main(String[] args) {
        char[] s = sc.nextLine().toCharArray();
        char[] t = sc.nextLine().toCharArray();

        int cnt = 0;
        for(int i=0; i<s.length; i++) {
            if(s[i] != t[i]) cnt++;
        }
        System.out.println(cnt);
    }
} import java.util.Scanner; Scanner java.util public class Main {
    static Scanner sc = new Scanner(System.in);
    public static void main(String[] args) {
        char[] s = sc.nextLine().toCharArray();
        char[] t = sc.nextLine().toCharArray();

        int cnt = 0;
        for(int i=0; i<s.length; i++) {
            if(s[i] != t[i]) cnt++;
        }
        System.out.println(cnt);
    }
} Main static Scanner sc = new Scanner(System.in); sc new Scanner(System.in) public static void main(String[] args) {
        char[] s = sc.nextLine().toCharArray();
        char[] t = sc.nextLine().toCharArray();

        int cnt = 0;
        for(int i=0; i<s.length; i++) {
            if(s[i] != t[i]) cnt++;
        }
        System.out.println(cnt);
    } main {
        char[] s = sc.nextLine().toCharArray();
        char[] t = sc.nextLine().toCharArray();

        int cnt = 0;
        for(int i=0; i<s.length; i++) {
            if(s[i] != t[i]) cnt++;
        }
        System.out.println(cnt);
    } char[] s = sc.nextLine().toCharArray(); s sc.nextLine().toCharArray() sc.nextLine().toCharArray sc.nextLine() sc.nextLine sc char[] t = sc.nextLine().toCharArray(); t sc.nextLine().toCharArray() sc.nextLine().toCharArray sc.nextLine() sc.nextLine sc int cnt = 0; cnt 0 for(int i=0; i<s.length; i++) {
            if(s[i] != t[i]) cnt++;
        } int i=0; int i=0; i 0 i<s.length i s.length s s.length i++ i++ i {
            if(s[i] != t[i]) cnt++;
        } {
            if(s[i] != t[i]) cnt++;
        } if(s[i] != t[i]) cnt++; s[i] != t[i] s[i] s i t[i] t i cnt++ cnt System.out.println(cnt) System.out.println System.out System System.out cnt String[] args args public class Main {
    static Scanner sc = new Scanner(System.in);
    public static void main(String[] args) {
        char[] s = sc.nextLine().toCharArray();
        char[] t = sc.nextLine().toCharArray();

        int cnt = 0;
        for(int i=0; i<s.length; i++) {
            if(s[i] != t[i]) cnt++;
        }
        System.out.println(cnt);
    }
} public class Main {
    static Scanner sc = new Scanner(System.in);
    public static void main(String[] args) {
        char[] s = sc.nextLine().toCharArray();
        char[] t = sc.nextLine().toCharArray();

        int cnt = 0;
        for(int i=0; i<s.length; i++) {
            if(s[i] != t[i]) cnt++;
        }
        System.out.println(cnt);
    }
} Main
import java.util.Scanner;

public class Main {
    static Scanner sc = new Scanner(System.in);
    public static void main(String[] args) {
        char[] s = sc.nextLine().toCharArray();
        char[] t = sc.nextLine().toCharArray();

        int cnt = 0;
        for(int i=0; i<s.length; i++) {
            if(s[i] != t[i]) cnt++;
        }
        System.out.println(cnt);
    }
}
