import java.util.*;
    public class Main{
        public static void main(String[] args) {
            Scanner sc = new Scanner(System.in);
            String s = sc.nextLine();
            String t = sc.nextLine();
            int count=0;
            for (int i=1;i <= s.length(); i++) {
                if(!s.substring(i-1,i).equals(t.substring(i-1,i))){
                    count++;
                }
            }
          	System.out.println(count);
        }
    } import java.util.*; util.* java public class Main{
        public static void main(String[] args) {
            Scanner sc = new Scanner(System.in);
            String s = sc.nextLine();
            String t = sc.nextLine();
            int count=0;
            for (int i=1;i <= s.length(); i++) {
                if(!s.substring(i-1,i).equals(t.substring(i-1,i))){
                    count++;
                }
            }
          	System.out.println(count);
        }
    } Main public static void main(String[] args) {
            Scanner sc = new Scanner(System.in);
            String s = sc.nextLine();
            String t = sc.nextLine();
            int count=0;
            for (int i=1;i <= s.length(); i++) {
                if(!s.substring(i-1,i).equals(t.substring(i-1,i))){
                    count++;
                }
            }
          	System.out.println(count);
        } main {
            Scanner sc = new Scanner(System.in);
            String s = sc.nextLine();
            String t = sc.nextLine();
            int count=0;
            for (int i=1;i <= s.length(); i++) {
                if(!s.substring(i-1,i).equals(t.substring(i-1,i))){
                    count++;
                }
            }
          	System.out.println(count);
        } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String s = sc.nextLine(); s sc.nextLine() sc.nextLine sc String t = sc.nextLine(); t sc.nextLine() sc.nextLine sc int count=0; count 0 for (int i=1;i <= s.length(); i++) {
                if(!s.substring(i-1,i).equals(t.substring(i-1,i))){
                    count++;
                }
            } int i=1; int i=1; i 1 i <= s.length() i s.length() s.length s i++ i++ i {
                if(!s.substring(i-1,i).equals(t.substring(i-1,i))){
                    count++;
                }
            } {
                if(!s.substring(i-1,i).equals(t.substring(i-1,i))){
                    count++;
                }
            } if(!s.substring(i-1,i).equals(t.substring(i-1,i))){
                    count++;
                } !s.substring(i-1,i).equals(t.substring(i-1,i)) s.substring(i-1,i).equals(t.substring(i-1,i)) s.substring(i-1,i).equals s.substring(i-1,i) s.substring s i-1 i 1 i t.substring(i-1,i) t.substring t i-1 i 1 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 sc = new Scanner(System.in);
            String s = sc.nextLine();
            String t = sc.nextLine();
            int count=0;
            for (int i=1;i <= s.length(); i++) {
                if(!s.substring(i-1,i).equals(t.substring(i-1,i))){
                    count++;
                }
            }
          	System.out.println(count);
        }
    } public class Main{
        public static void main(String[] args) {
            Scanner sc = new Scanner(System.in);
            String s = sc.nextLine();
            String t = sc.nextLine();
            int count=0;
            for (int i=1;i <= s.length(); i++) {
                if(!s.substring(i-1,i).equals(t.substring(i-1,i))){
                    count++;
                }
            }
          	System.out.println(count);
        }
    } Main
import java.util.*;
    public class Main{
        public static void main(String[] args) {
            Scanner sc = new Scanner(System.in);
            String s = sc.nextLine();
            String t = sc.nextLine();
            int count=0;
            for (int i=1;i <= s.length(); i++) {
                if(!s.substring(i-1,i).equals(t.substring(i-1,i))){
                    count++;
                }
            }
          	System.out.println(count);
        }
    }