import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String line = sc.nextLine();
        String[] inputA = line.split("");
        line = sc.nextLine();
        String[] inputB = line.split("");
      
      int count =0;
      for(int i=0;i<inputA.length;i++){
        if(!inputA[i].equals(inputB[i])){
          count++;
        }
      }
       System.out.println(String.valueOf(count));
    }
} import java.util.*; util.* java public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String line = sc.nextLine();
        String[] inputA = line.split("");
        line = sc.nextLine();
        String[] inputB = line.split("");
      
      int count =0;
      for(int i=0;i<inputA.length;i++){
        if(!inputA[i].equals(inputB[i])){
          count++;
        }
      }
       System.out.println(String.valueOf(count));
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String line = sc.nextLine();
        String[] inputA = line.split("");
        line = sc.nextLine();
        String[] inputB = line.split("");
      
      int count =0;
      for(int i=0;i<inputA.length;i++){
        if(!inputA[i].equals(inputB[i])){
          count++;
        }
      }
       System.out.println(String.valueOf(count));
    } main {
        Scanner sc = new Scanner(System.in);
        String line = sc.nextLine();
        String[] inputA = line.split("");
        line = sc.nextLine();
        String[] inputB = line.split("");
      
      int count =0;
      for(int i=0;i<inputA.length;i++){
        if(!inputA[i].equals(inputB[i])){
          count++;
        }
      }
       System.out.println(String.valueOf(count));
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String line = sc.nextLine(); line sc.nextLine() sc.nextLine sc String[] inputA = line.split(""); inputA line.split("") line.split line "" line = sc.nextLine() line sc.nextLine() sc.nextLine sc String[] inputB = line.split(""); inputB line.split("") line.split line "" int count =0; count 0 for(int i=0;i<inputA.length;i++){
        if(!inputA[i].equals(inputB[i])){
          count++;
        }
      } int i=0; int i=0; i 0 i<inputA.length i inputA.length inputA inputA.length i++ i++ i {
        if(!inputA[i].equals(inputB[i])){
          count++;
        }
      } {
        if(!inputA[i].equals(inputB[i])){
          count++;
        }
      } if(!inputA[i].equals(inputB[i])){
          count++;
        } !inputA[i].equals(inputB[i]) inputA[i].equals(inputB[i]) inputA[i].equals inputA[i] inputA i inputB[i] inputB i {
          count++;
        } count++ count System.out.println(String.valueOf(count)) System.out.println System.out System System.out String.valueOf(count) String.valueOf String count String[] args args public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String line = sc.nextLine();
        String[] inputA = line.split("");
        line = sc.nextLine();
        String[] inputB = line.split("");
      
      int count =0;
      for(int i=0;i<inputA.length;i++){
        if(!inputA[i].equals(inputB[i])){
          count++;
        }
      }
       System.out.println(String.valueOf(count));
    }
} public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String line = sc.nextLine();
        String[] inputA = line.split("");
        line = sc.nextLine();
        String[] inputB = line.split("");
      
      int count =0;
      for(int i=0;i<inputA.length;i++){
        if(!inputA[i].equals(inputB[i])){
          count++;
        }
      }
       System.out.println(String.valueOf(count));
    }
} Main
import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String line = sc.nextLine();
        String[] inputA = line.split("");
        line = sc.nextLine();
        String[] inputB = line.split("");
      
      int count =0;
      for(int i=0;i<inputA.length;i++){
        if(!inputA[i].equals(inputB[i])){
          count++;
        }
      }
       System.out.println(String.valueOf(count));
    }
}