import java.util.*; 

class Main{
  public static void main(String args[]){
    Scanner scn = new Scanner(System.in);
    int count =0;
    String one =scn.next();
    String two =scn.next();
    for(int i=0;i<one.length();i++){
      if(one.charAt(i)!=two.charAt(i)){
        count++;
        continue;
      }
    }   
    System.out.println(count);
  }
} import java.util.*; util.* java class Main{
  public static void main(String args[]){
    Scanner scn = new Scanner(System.in);
    int count =0;
    String one =scn.next();
    String two =scn.next();
    for(int i=0;i<one.length();i++){
      if(one.charAt(i)!=two.charAt(i)){
        count++;
        continue;
      }
    }   
    System.out.println(count);
  }
} Main public static void main(String args[]){
    Scanner scn = new Scanner(System.in);
    int count =0;
    String one =scn.next();
    String two =scn.next();
    for(int i=0;i<one.length();i++){
      if(one.charAt(i)!=two.charAt(i)){
        count++;
        continue;
      }
    }   
    System.out.println(count);
  } main {
    Scanner scn = new Scanner(System.in);
    int count =0;
    String one =scn.next();
    String two =scn.next();
    for(int i=0;i<one.length();i++){
      if(one.charAt(i)!=two.charAt(i)){
        count++;
        continue;
      }
    }   
    System.out.println(count);
  } Scanner scn = new Scanner(System.in); scn new Scanner(System.in) int count =0; count 0 String one =scn.next(); one scn.next() scn.next scn String two =scn.next(); two scn.next() scn.next scn for(int i=0;i<one.length();i++){
      if(one.charAt(i)!=two.charAt(i)){
        count++;
        continue;
      }
    } int i=0; int i=0; i 0 i<one.length() i one.length() one.length one i++ i++ i {
      if(one.charAt(i)!=two.charAt(i)){
        count++;
        continue;
      }
    } {
      if(one.charAt(i)!=two.charAt(i)){
        count++;
        continue;
      }
    } if(one.charAt(i)!=two.charAt(i)){
        count++;
        continue;
      } one.charAt(i)!=two.charAt(i) one.charAt(i) one.charAt one i two.charAt(i) two.charAt two i {
        count++;
        continue;
      } count++ count continue; System.out.println(count) System.out.println System.out System System.out count String args[] args
import java.util.*; 

class Main{
  public static void main(String args[]){
    Scanner scn = new Scanner(System.in);
    int count =0;
    String one =scn.next();
    String two =scn.next();
    for(int i=0;i<one.length();i++){
      if(one.charAt(i)!=two.charAt(i)){
        count++;
        continue;
      }
    }   
    System.out.println(count);
  }
}