import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;
public class Main {
 public static void main(String[] args) throws IOException {
   BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
   String S = reader.readLine();
   String T = reader.readLine();
   int count = 0;
   for (int i = 0; i < S.length(); i++) {
     if (S.charAt(i) != T.charAt(i)) count += 1;
   }
   System.out.println(count);
 }
} import java.io.BufferedReader; BufferedReader java.io import java.io.InputStreamReader; InputStreamReader java.io import java.io.IOException; IOException java.io public class Main {
 public static void main(String[] args) throws IOException {
   BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
   String S = reader.readLine();
   String T = reader.readLine();
   int count = 0;
   for (int i = 0; i < S.length(); i++) {
     if (S.charAt(i) != T.charAt(i)) count += 1;
   }
   System.out.println(count);
 }
} Main public static void main(String[] args) throws IOException {
   BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
   String S = reader.readLine();
   String T = reader.readLine();
   int count = 0;
   for (int i = 0; i < S.length(); i++) {
     if (S.charAt(i) != T.charAt(i)) count += 1;
   }
   System.out.println(count);
 } main {
   BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
   String S = reader.readLine();
   String T = reader.readLine();
   int count = 0;
   for (int i = 0; i < S.length(); i++) {
     if (S.charAt(i) != T.charAt(i)) count += 1;
   }
   System.out.println(count);
 } BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); reader new BufferedReader(new InputStreamReader(System.in)) String S = reader.readLine(); S reader.readLine() reader.readLine reader String T = reader.readLine(); T reader.readLine() reader.readLine reader int count = 0; count 0 for (int i = 0; i < S.length(); i++) {
     if (S.charAt(i) != T.charAt(i)) count += 1;
   } int i = 0; int i = 0; i 0 i < S.length() i S.length() S.length S i++ i++ i {
     if (S.charAt(i) != T.charAt(i)) count += 1;
   } {
     if (S.charAt(i) != T.charAt(i)) count += 1;
   } if (S.charAt(i) != T.charAt(i)) count += 1; S.charAt(i) != T.charAt(i) S.charAt(i) S.charAt S i T.charAt(i) T.charAt T i count += 1 count 1 System.out.println(count) System.out.println System.out System System.out count String[] args args public class Main {
 public static void main(String[] args) throws IOException {
   BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
   String S = reader.readLine();
   String T = reader.readLine();
   int count = 0;
   for (int i = 0; i < S.length(); i++) {
     if (S.charAt(i) != T.charAt(i)) count += 1;
   }
   System.out.println(count);
 }
} public class Main {
 public static void main(String[] args) throws IOException {
   BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
   String S = reader.readLine();
   String T = reader.readLine();
   int count = 0;
   for (int i = 0; i < S.length(); i++) {
     if (S.charAt(i) != T.charAt(i)) count += 1;
   }
   System.out.println(count);
 }
} Main
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;
public class Main {
 public static void main(String[] args) throws IOException {
   BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
   String S = reader.readLine();
   String T = reader.readLine();
   int count = 0;
   for (int i = 0; i < S.length(); i++) {
     if (S.charAt(i) != T.charAt(i)) count += 1;
   }
   System.out.println(count);
 }
}
