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

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

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

        int res=s.length;
        for(int i=0; i<s.length; i++){
            if(s[i] == t[i]){
                res--;
            }
        }
        System.out.println(res);
        } main {
		Scanner sc = new Scanner(System.in);
        char[] s = sc.next().toCharArray();
        char[] t = sc.next().toCharArray();

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

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

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

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