import java.util.*;

class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
      int counter  =0;
       String a = sc.next();
       String b = sc.next();
       String[] aa = a.split("");
      String[] bb = b.split("");
      String[] cc = new String[aa.length];
      for(int i =0; i< aa.length;i++){
      	if(aa[i].equals(bb[i])){
          
        }else{
        	counter++;
           
        }
      }
      System.out.println(counter);
      
    }
} import java.util.*; util.* java class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
      int counter  =0;
       String a = sc.next();
       String b = sc.next();
       String[] aa = a.split("");
      String[] bb = b.split("");
      String[] cc = new String[aa.length];
      for(int i =0; i< aa.length;i++){
      	if(aa[i].equals(bb[i])){
          
        }else{
        	counter++;
           
        }
      }
      System.out.println(counter);
      
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
      int counter  =0;
       String a = sc.next();
       String b = sc.next();
       String[] aa = a.split("");
      String[] bb = b.split("");
      String[] cc = new String[aa.length];
      for(int i =0; i< aa.length;i++){
      	if(aa[i].equals(bb[i])){
          
        }else{
        	counter++;
           
        }
      }
      System.out.println(counter);
      
    } main {
        Scanner sc = new Scanner(System.in);
      int counter  =0;
       String a = sc.next();
       String b = sc.next();
       String[] aa = a.split("");
      String[] bb = b.split("");
      String[] cc = new String[aa.length];
      for(int i =0; i< aa.length;i++){
      	if(aa[i].equals(bb[i])){
          
        }else{
        	counter++;
           
        }
      }
      System.out.println(counter);
      
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int counter  =0; counter 0 String a = sc.next(); a sc.next() sc.next sc String b = sc.next(); b sc.next() sc.next sc String[] aa = a.split(""); aa a.split("") a.split a "" String[] bb = b.split(""); bb b.split("") b.split b "" String[] cc = new String[aa.length]; cc new String[aa.length] aa.length aa aa.length for(int i =0; i< aa.length;i++){
      	if(aa[i].equals(bb[i])){
          
        }else{
        	counter++;
           
        }
      } int i =0; int i =0; i 0 i< aa.length i aa.length aa aa.length i++ i++ i {
      	if(aa[i].equals(bb[i])){
          
        }else{
        	counter++;
           
        }
      } {
      	if(aa[i].equals(bb[i])){
          
        }else{
        	counter++;
           
        }
      } if(aa[i].equals(bb[i])){
          
        }else{
        	counter++;
           
        } aa[i].equals(bb[i]) aa[i].equals aa[i] aa i bb[i] bb i {
          
        } {
        	counter++;
           
        } counter++ counter System.out.println(counter) System.out.println System.out System System.out counter String[] args args
import java.util.*;

class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
      int counter  =0;
       String a = sc.next();
       String b = sc.next();
       String[] aa = a.split("");
      String[] bb = b.split("");
      String[] cc = new String[aa.length];
      for(int i =0; i< aa.length;i++){
      	if(aa[i].equals(bb[i])){
          
        }else{
        	counter++;
           
        }
      }
      System.out.println(counter);
      
    }
}