import java.util.Scanner;
public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String T = sc.next();
        int cnt = 0;
        for(int i=0; i<S.length(); i++){
          if(S.charAt(i) != T.charAt(i)){
            cnt++;
          } else {
            continue;
          }
        }
        System.out.println(cnt);
   }
} import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String T = sc.next();
        int cnt = 0;
        for(int i=0; i<S.length(); i++){
          if(S.charAt(i) != T.charAt(i)){
            cnt++;
          } else {
            continue;
          }
        }
        System.out.println(cnt);
   }
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String T = sc.next();
        int cnt = 0;
        for(int i=0; i<S.length(); i++){
          if(S.charAt(i) != T.charAt(i)){
            cnt++;
          } else {
            continue;
          }
        }
        System.out.println(cnt);
   } main {
		Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String T = sc.next();
        int cnt = 0;
        for(int i=0; i<S.length(); i++){
          if(S.charAt(i) != T.charAt(i)){
            cnt++;
          } else {
            continue;
          }
        }
        System.out.println(cnt);
   } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String S = sc.next(); S sc.next() sc.next sc String T = sc.next(); T sc.next() sc.next sc int cnt = 0; cnt 0 for(int i=0; i<S.length(); i++){
          if(S.charAt(i) != T.charAt(i)){
            cnt++;
          } else {
            continue;
          }
        } 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)){
            cnt++;
          } else {
            continue;
          }
        } {
          if(S.charAt(i) != T.charAt(i)){
            cnt++;
          } else {
            continue;
          }
        } if(S.charAt(i) != T.charAt(i)){
            cnt++;
          } else {
            continue;
          } S.charAt(i) != T.charAt(i) S.charAt(i) S.charAt S i T.charAt(i) T.charAt T i {
            cnt++;
          } cnt++ cnt {
            continue;
          } continue; System.out.println(cnt) System.out.println System.out System System.out cnt String[] args args public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String T = sc.next();
        int cnt = 0;
        for(int i=0; i<S.length(); i++){
          if(S.charAt(i) != T.charAt(i)){
            cnt++;
          } else {
            continue;
          }
        }
        System.out.println(cnt);
   }
} public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String T = sc.next();
        int cnt = 0;
        for(int i=0; i<S.length(); i++){
          if(S.charAt(i) != T.charAt(i)){
            cnt++;
          } else {
            continue;
          }
        }
        System.out.println(cnt);
   }
} Main
import java.util.Scanner;
public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String T = sc.next();
        int cnt = 0;
        for(int i=0; i<S.length(); i++){
          if(S.charAt(i) != T.charAt(i)){
            cnt++;
          } else {
            continue;
          }
        }
        System.out.println(cnt);
   }
}