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 sum=0;
        for(int i=0;i<s.length;i++){
            sum+=(s[i]==t[i])?0:1;
        }
        System.out.println(sum);
    }
} 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 sum=0;
        for(int i=0;i<s.length;i++){
            sum+=(s[i]==t[i])?0:1;
        }
        System.out.println(sum);
    }
} Main public static void main(String[]args){
        Scanner sc=new Scanner(System.in);
        char[]s=sc.next().toCharArray();
        char[]t=sc.next().toCharArray();
        int sum=0;
        for(int i=0;i<s.length;i++){
            sum+=(s[i]==t[i])?0:1;
        }
        System.out.println(sum);
    } main {
        Scanner sc=new Scanner(System.in);
        char[]s=sc.next().toCharArray();
        char[]t=sc.next().toCharArray();
        int sum=0;
        for(int i=0;i<s.length;i++){
            sum+=(s[i]==t[i])?0:1;
        }
        System.out.println(sum);
    } 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 sum=0; sum 0 for(int i=0;i<s.length;i++){
            sum+=(s[i]==t[i])?0:1;
        } int i=0; int i=0; i 0 i<s.length i s.length s s.length i++ i++ i {
            sum+=(s[i]==t[i])?0:1;
        } {
            sum+=(s[i]==t[i])?0:1;
        } sum+=(s[i]==t[i])?0:1 sum (s[i]==t[i])?0:1 (s[i]==t[i]) s[i] s i t[i] t i 0 1 System.out.println(sum) System.out.println System.out System System.out sum 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 sum=0;
        for(int i=0;i<s.length;i++){
            sum+=(s[i]==t[i])?0:1;
        }
        System.out.println(sum);
    }
} 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 sum=0;
        for(int i=0;i<s.length;i++){
            sum+=(s[i]==t[i])?0:1;
        }
        System.out.println(sum);
    }
} 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 sum=0;
        for(int i=0;i<s.length;i++){
            sum+=(s[i]==t[i])?0:1;
        }
        System.out.println(sum);
    }
}
