import java.util.*;
import java.io.*;
public class Main{
   public static void main(String[] main) throws Exception{
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
      StringTokenizer st = new StringTokenizer(br.readLine());
      PrintWriter out = new PrintWriter(System.out);
      String s = st.nextToken();
      st = new StringTokenizer(br.readLine());
      String t = st.nextToken();
     int count = 0;
     for(int i = 0; i < s.length(); i++)
       if(s.charAt(i) != t.charAt(i))
         count++;
     out.println(count);
      out.close();
   }
} import java.util.*; util.* java import java.io.*; io.* java public class Main{
   public static void main(String[] main) throws Exception{
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
      StringTokenizer st = new StringTokenizer(br.readLine());
      PrintWriter out = new PrintWriter(System.out);
      String s = st.nextToken();
      st = new StringTokenizer(br.readLine());
      String t = st.nextToken();
     int count = 0;
     for(int i = 0; i < s.length(); i++)
       if(s.charAt(i) != t.charAt(i))
         count++;
     out.println(count);
      out.close();
   }
} Main public static void main(String[] main) throws Exception{
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
      StringTokenizer st = new StringTokenizer(br.readLine());
      PrintWriter out = new PrintWriter(System.out);
      String s = st.nextToken();
      st = new StringTokenizer(br.readLine());
      String t = st.nextToken();
     int count = 0;
     for(int i = 0; i < s.length(); i++)
       if(s.charAt(i) != t.charAt(i))
         count++;
     out.println(count);
      out.close();
   } main {
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
      StringTokenizer st = new StringTokenizer(br.readLine());
      PrintWriter out = new PrintWriter(System.out);
      String s = st.nextToken();
      st = new StringTokenizer(br.readLine());
      String t = st.nextToken();
     int count = 0;
     for(int i = 0; i < s.length(); i++)
       if(s.charAt(i) != t.charAt(i))
         count++;
     out.println(count);
      out.close();
   } BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); br new BufferedReader(new InputStreamReader(System.in)) StringTokenizer st = new StringTokenizer(br.readLine()); st new StringTokenizer(br.readLine()) PrintWriter out = new PrintWriter(System.out); out new PrintWriter(System.out) String s = st.nextToken(); s st.nextToken() st.nextToken st st = new StringTokenizer(br.readLine()) st new StringTokenizer(br.readLine()) String t = st.nextToken(); t st.nextToken() st.nextToken st int count = 0; count 0 for(int i = 0; i < s.length(); i++)
       if(s.charAt(i) != t.charAt(i))
         count++; 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++; if(s.charAt(i) != t.charAt(i))
         count++; s.charAt(i) != t.charAt(i) s.charAt(i) s.charAt s i t.charAt(i) t.charAt t i count++ count out.println(count) out.println out count out.close() out.close out String[] main main public class Main{
   public static void main(String[] main) throws Exception{
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
      StringTokenizer st = new StringTokenizer(br.readLine());
      PrintWriter out = new PrintWriter(System.out);
      String s = st.nextToken();
      st = new StringTokenizer(br.readLine());
      String t = st.nextToken();
     int count = 0;
     for(int i = 0; i < s.length(); i++)
       if(s.charAt(i) != t.charAt(i))
         count++;
     out.println(count);
      out.close();
   }
} public class Main{
   public static void main(String[] main) throws Exception{
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
      StringTokenizer st = new StringTokenizer(br.readLine());
      PrintWriter out = new PrintWriter(System.out);
      String s = st.nextToken();
      st = new StringTokenizer(br.readLine());
      String t = st.nextToken();
     int count = 0;
     for(int i = 0; i < s.length(); i++)
       if(s.charAt(i) != t.charAt(i))
         count++;
     out.println(count);
      out.close();
   }
} Main
import java.util.*;
import java.io.*;
public class Main{
   public static void main(String[] main) throws Exception{
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
      StringTokenizer st = new StringTokenizer(br.readLine());
      PrintWriter out = new PrintWriter(System.out);
      String s = st.nextToken();
      st = new StringTokenizer(br.readLine());
      String t = st.nextToken();
     int count = 0;
     for(int i = 0; i < s.length(); i++)
       if(s.charAt(i) != t.charAt(i))
         count++;
     out.println(count);
      out.close();
   }
}