import java.util.*;
public class Main {
	public static void main(String[] args){
       Scanner sc = new Scanner(System.in);
      
      //文字列Sの取得
      String S = sc.nextLine();
      //文字列Tの取得
      String T = sc.nextLine();
 
      //置き換え回数
      int count = 0;
      
      for (int i = 0; i < S.length(); i++) {
            char s = S.charAt(i);
            char t = T.charAt(i);
            
            if (!(s == t)) {
               count++;
            }
      }
 
		System.out.println(count);
    }
} import java.util.*; util.* java public class Main {
	public static void main(String[] args){
       Scanner sc = new Scanner(System.in);
      
      //文字列Sの取得
      String S = sc.nextLine();
      //文字列Tの取得
      String T = sc.nextLine();
 
      //置き換え回数
      int count = 0;
      
      for (int i = 0; i < S.length(); i++) {
            char s = S.charAt(i);
            char t = T.charAt(i);
            
            if (!(s == t)) {
               count++;
            }
      }
 
		System.out.println(count);
    }
} Main public static void main(String[] args){
       Scanner sc = new Scanner(System.in);
      
      //文字列Sの取得
      String S = sc.nextLine();
      //文字列Tの取得
      String T = sc.nextLine();
 
      //置き換え回数
      int count = 0;
      
      for (int i = 0; i < S.length(); i++) {
            char s = S.charAt(i);
            char t = T.charAt(i);
            
            if (!(s == t)) {
               count++;
            }
      }
 
		System.out.println(count);
    } main {
       Scanner sc = new Scanner(System.in);
      
      //文字列Sの取得
      String S = sc.nextLine();
      //文字列Tの取得
      String T = sc.nextLine();
 
      //置き換え回数
      int count = 0;
      
      for (int i = 0; i < S.length(); i++) {
            char s = S.charAt(i);
            char t = T.charAt(i);
            
            if (!(s == t)) {
               count++;
            }
      }
 
		System.out.println(count);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String S = sc.nextLine(); S sc.nextLine() sc.nextLine sc String T = sc.nextLine(); T sc.nextLine() sc.nextLine sc int count = 0; count 0 for (int i = 0; i < S.length(); i++) {
            char s = S.charAt(i);
            char t = T.charAt(i);
            
            if (!(s == t)) {
               count++;
            }
      } int i = 0; int i = 0; i 0 i < S.length() i S.length() S.length S i++ i++ i {
            char s = S.charAt(i);
            char t = T.charAt(i);
            
            if (!(s == t)) {
               count++;
            }
      } {
            char s = S.charAt(i);
            char t = T.charAt(i);
            
            if (!(s == t)) {
               count++;
            }
      } char s = S.charAt(i); s S.charAt(i) S.charAt S i char t = T.charAt(i); t T.charAt(i) T.charAt T i if (!(s == t)) {
               count++;
            } !(s == t) (s == t) s t {
               count++;
            } count++ count 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){
       Scanner sc = new Scanner(System.in);
      
      //文字列Sの取得
      String S = sc.nextLine();
      //文字列Tの取得
      String T = sc.nextLine();
 
      //置き換え回数
      int count = 0;
      
      for (int i = 0; i < S.length(); i++) {
            char s = S.charAt(i);
            char t = T.charAt(i);
            
            if (!(s == t)) {
               count++;
            }
      }
 
		System.out.println(count);
    }
} public class Main {
	public static void main(String[] args){
       Scanner sc = new Scanner(System.in);
      
      //文字列Sの取得
      String S = sc.nextLine();
      //文字列Tの取得
      String T = sc.nextLine();
 
      //置き換え回数
      int count = 0;
      
      for (int i = 0; i < S.length(); i++) {
            char s = S.charAt(i);
            char t = T.charAt(i);
            
            if (!(s == t)) {
               count++;
            }
      }
 
		System.out.println(count);
    }
} Main
import java.util.*;
public class Main {
	public static void main(String[] args){
       Scanner sc = new Scanner(System.in);
      
      //文字列Sの取得
      String S = sc.nextLine();
      //文字列Tの取得
      String T = sc.nextLine();
 
      //置き換え回数
      int count = 0;
      
      for (int i = 0; i < S.length(); i++) {
            char s = S.charAt(i);
            char t = T.charAt(i);
            
            if (!(s == t)) {
               count++;
            }
      }
 
		System.out.println(count);
    }
}