import java.util.*;
import java.io.*;
class Main{
  public static void main(String[] args){
    try{
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
      String s = br.readLine();
      String t = br.readLine();
      StringBuilder sb1 = new StringBuilder(t);
      //System.out.println(s);
      int ans = 0;
      for(int i=0;i<s.length();i++){
        if(s.equals(t)){
          break;
        }else{
          char s1 = s.charAt(i);
          char t1 = t.charAt(i);
          if(!(s1==t1)){
            ans++;
            sb1.setCharAt(i, s1);
         }
       }
      }
       System.out.println(ans);
    }catch(IOException e){
       System.out.println(e);
    }
  }
} import java.util.*; util.* java import java.io.*; io.* java class Main{
  public static void main(String[] args){
    try{
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
      String s = br.readLine();
      String t = br.readLine();
      StringBuilder sb1 = new StringBuilder(t);
      //System.out.println(s);
      int ans = 0;
      for(int i=0;i<s.length();i++){
        if(s.equals(t)){
          break;
        }else{
          char s1 = s.charAt(i);
          char t1 = t.charAt(i);
          if(!(s1==t1)){
            ans++;
            sb1.setCharAt(i, s1);
         }
       }
      }
       System.out.println(ans);
    }catch(IOException e){
       System.out.println(e);
    }
  }
} Main public static void main(String[] args){
    try{
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
      String s = br.readLine();
      String t = br.readLine();
      StringBuilder sb1 = new StringBuilder(t);
      //System.out.println(s);
      int ans = 0;
      for(int i=0;i<s.length();i++){
        if(s.equals(t)){
          break;
        }else{
          char s1 = s.charAt(i);
          char t1 = t.charAt(i);
          if(!(s1==t1)){
            ans++;
            sb1.setCharAt(i, s1);
         }
       }
      }
       System.out.println(ans);
    }catch(IOException e){
       System.out.println(e);
    }
  } main {
    try{
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
      String s = br.readLine();
      String t = br.readLine();
      StringBuilder sb1 = new StringBuilder(t);
      //System.out.println(s);
      int ans = 0;
      for(int i=0;i<s.length();i++){
        if(s.equals(t)){
          break;
        }else{
          char s1 = s.charAt(i);
          char t1 = t.charAt(i);
          if(!(s1==t1)){
            ans++;
            sb1.setCharAt(i, s1);
         }
       }
      }
       System.out.println(ans);
    }catch(IOException e){
       System.out.println(e);
    }
  } try{
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
      String s = br.readLine();
      String t = br.readLine();
      StringBuilder sb1 = new StringBuilder(t);
      //System.out.println(s);
      int ans = 0;
      for(int i=0;i<s.length();i++){
        if(s.equals(t)){
          break;
        }else{
          char s1 = s.charAt(i);
          char t1 = t.charAt(i);
          if(!(s1==t1)){
            ans++;
            sb1.setCharAt(i, s1);
         }
       }
      }
       System.out.println(ans);
    }catch(IOException e){
       System.out.println(e);
    } catch(IOException e){
       System.out.println(e);
    } IOException e {
       System.out.println(e);
    } System.out.println(e) System.out.println System.out System System.out e {
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
      String s = br.readLine();
      String t = br.readLine();
      StringBuilder sb1 = new StringBuilder(t);
      //System.out.println(s);
      int ans = 0;
      for(int i=0;i<s.length();i++){
        if(s.equals(t)){
          break;
        }else{
          char s1 = s.charAt(i);
          char t1 = t.charAt(i);
          if(!(s1==t1)){
            ans++;
            sb1.setCharAt(i, s1);
         }
       }
      }
       System.out.println(ans);
    } BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); br new BufferedReader(new InputStreamReader(System.in)) String s = br.readLine(); s br.readLine() br.readLine br String t = br.readLine(); t br.readLine() br.readLine br StringBuilder sb1 = new StringBuilder(t); sb1 new StringBuilder(t) int ans = 0; ans 0 for(int i=0;i<s.length();i++){
        if(s.equals(t)){
          break;
        }else{
          char s1 = s.charAt(i);
          char t1 = t.charAt(i);
          if(!(s1==t1)){
            ans++;
            sb1.setCharAt(i, s1);
         }
       }
      } int i=0; int i=0; i 0 i<s.length() i s.length() s.length s i++ i++ i {
        if(s.equals(t)){
          break;
        }else{
          char s1 = s.charAt(i);
          char t1 = t.charAt(i);
          if(!(s1==t1)){
            ans++;
            sb1.setCharAt(i, s1);
         }
       }
      } {
        if(s.equals(t)){
          break;
        }else{
          char s1 = s.charAt(i);
          char t1 = t.charAt(i);
          if(!(s1==t1)){
            ans++;
            sb1.setCharAt(i, s1);
         }
       }
      } if(s.equals(t)){
          break;
        }else{
          char s1 = s.charAt(i);
          char t1 = t.charAt(i);
          if(!(s1==t1)){
            ans++;
            sb1.setCharAt(i, s1);
         }
       } s.equals(t) s.equals s t {
          break;
        } break; {
          char s1 = s.charAt(i);
          char t1 = t.charAt(i);
          if(!(s1==t1)){
            ans++;
            sb1.setCharAt(i, s1);
         }
       } char s1 = s.charAt(i); s1 s.charAt(i) s.charAt s i char t1 = t.charAt(i); t1 t.charAt(i) t.charAt t i if(!(s1==t1)){
            ans++;
            sb1.setCharAt(i, s1);
         } !(s1==t1) (s1==t1) s1 t1 {
            ans++;
            sb1.setCharAt(i, s1);
         } ans++ ans sb1.setCharAt(i, s1) sb1.setCharAt sb1 i s1 System.out.println(ans) System.out.println System.out System System.out ans String[] args args
import java.util.*;
import java.io.*;
class Main{
  public static void main(String[] args){
    try{
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
      String s = br.readLine();
      String t = br.readLine();
      StringBuilder sb1 = new StringBuilder(t);
      //System.out.println(s);
      int ans = 0;
      for(int i=0;i<s.length();i++){
        if(s.equals(t)){
          break;
        }else{
          char s1 = s.charAt(i);
          char t1 = t.charAt(i);
          if(!(s1==t1)){
            ans++;
            sb1.setCharAt(i, s1);
         }
       }
      }
       System.out.println(ans);
    }catch(IOException e){
       System.out.println(e);
    }
  }
}