import java.util.*;
public class Main{
  public static void main(String[] args){
    Scanner sc =new Scanner(System.in);
    String S =sc.next();
    String s[] =S.split("",0);
    String T =sc.next();
    String t[] =T.split("",0);
    int N =S.length();
    int a=N;
    for(int i=0;i<N;i++){
      if(s[i].equals(t[i])){a=a-1;}}
    System.out.println(a);
  }
} import java.util.*; util.* java public class Main{
  public static void main(String[] args){
    Scanner sc =new Scanner(System.in);
    String S =sc.next();
    String s[] =S.split("",0);
    String T =sc.next();
    String t[] =T.split("",0);
    int N =S.length();
    int a=N;
    for(int i=0;i<N;i++){
      if(s[i].equals(t[i])){a=a-1;}}
    System.out.println(a);
  }
} Main public static void main(String[] args){
    Scanner sc =new Scanner(System.in);
    String S =sc.next();
    String s[] =S.split("",0);
    String T =sc.next();
    String t[] =T.split("",0);
    int N =S.length();
    int a=N;
    for(int i=0;i<N;i++){
      if(s[i].equals(t[i])){a=a-1;}}
    System.out.println(a);
  } main {
    Scanner sc =new Scanner(System.in);
    String S =sc.next();
    String s[] =S.split("",0);
    String T =sc.next();
    String t[] =T.split("",0);
    int N =S.length();
    int a=N;
    for(int i=0;i<N;i++){
      if(s[i].equals(t[i])){a=a-1;}}
    System.out.println(a);
  } Scanner sc =new Scanner(System.in); sc new Scanner(System.in) String S =sc.next(); S sc.next() sc.next sc String s[] =S.split("",0); s S.split("",0) S.split S "" 0 String T =sc.next(); T sc.next() sc.next sc String t[] =T.split("",0); t T.split("",0) T.split T "" 0 int N =S.length(); N S.length() S.length S int a=N; a N for(int i=0;i<N;i++){
      if(s[i].equals(t[i])){a=a-1;}} int i=0; int i=0; i 0 i<N i N i++ i++ i {
      if(s[i].equals(t[i])){a=a-1;}} {
      if(s[i].equals(t[i])){a=a-1;}} if(s[i].equals(t[i])){a=a-1;} s[i].equals(t[i]) s[i].equals s[i] s i t[i] t i {a=a-1;} a=a-1 a a-1 a 1 System.out.println(a) System.out.println System.out System System.out a String[] args args public class Main{
  public static void main(String[] args){
    Scanner sc =new Scanner(System.in);
    String S =sc.next();
    String s[] =S.split("",0);
    String T =sc.next();
    String t[] =T.split("",0);
    int N =S.length();
    int a=N;
    for(int i=0;i<N;i++){
      if(s[i].equals(t[i])){a=a-1;}}
    System.out.println(a);
  }
} public class Main{
  public static void main(String[] args){
    Scanner sc =new Scanner(System.in);
    String S =sc.next();
    String s[] =S.split("",0);
    String T =sc.next();
    String t[] =T.split("",0);
    int N =S.length();
    int a=N;
    for(int i=0;i<N;i++){
      if(s[i].equals(t[i])){a=a-1;}}
    System.out.println(a);
  }
} Main
import java.util.*;
public class Main{
  public static void main(String[] args){
    Scanner sc =new Scanner(System.in);
    String S =sc.next();
    String s[] =S.split("",0);
    String T =sc.next();
    String t[] =T.split("",0);
    int N =S.length();
    int a=N;
    for(int i=0;i<N;i++){
      if(s[i].equals(t[i])){a=a-1;}}
    System.out.println(a);
  }
}
