import java.util.*;
public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		
		// 文字列の入力
		String s1 = sc.next();
		String s2 = sc.next();
      int counter =  s1.length();
		for(int i = 0; i < s1.length() ; i++){
			if(s1.substring( i, i + 1).equals (s2.substring(i, i + 1))){
				counter -= 1;
			}	
		}
		// 出力
		System.out.println(counter);
	}
} import java.util.*; util.* java public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		
		// 文字列の入力
		String s1 = sc.next();
		String s2 = sc.next();
      int counter =  s1.length();
		for(int i = 0; i < s1.length() ; i++){
			if(s1.substring( i, i + 1).equals (s2.substring(i, i + 1))){
				counter -= 1;
			}	
		}
		// 出力
		System.out.println(counter);
	}
} Main public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		
		// 文字列の入力
		String s1 = sc.next();
		String s2 = sc.next();
      int counter =  s1.length();
		for(int i = 0; i < s1.length() ; i++){
			if(s1.substring( i, i + 1).equals (s2.substring(i, i + 1))){
				counter -= 1;
			}	
		}
		// 出力
		System.out.println(counter);
	} main {
		Scanner sc = new Scanner(System.in);
		
		// 文字列の入力
		String s1 = sc.next();
		String s2 = sc.next();
      int counter =  s1.length();
		for(int i = 0; i < s1.length() ; i++){
			if(s1.substring( i, i + 1).equals (s2.substring(i, i + 1))){
				counter -= 1;
			}	
		}
		// 出力
		System.out.println(counter);
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String s1 = sc.next(); s1 sc.next() sc.next sc String s2 = sc.next(); s2 sc.next() sc.next sc int counter =  s1.length(); counter s1.length() s1.length s1 for(int i = 0; i < s1.length() ; i++){
			if(s1.substring( i, i + 1).equals (s2.substring(i, i + 1))){
				counter -= 1;
			}	
		} int i = 0; int i = 0; i 0 i < s1.length() i s1.length() s1.length s1 i++ i++ i {
			if(s1.substring( i, i + 1).equals (s2.substring(i, i + 1))){
				counter -= 1;
			}	
		} {
			if(s1.substring( i, i + 1).equals (s2.substring(i, i + 1))){
				counter -= 1;
			}	
		} if(s1.substring( i, i + 1).equals (s2.substring(i, i + 1))){
				counter -= 1;
			} s1.substring( i, i + 1).equals (s2.substring(i, i + 1)) s1.substring( i, i + 1).equals s1.substring( i, i + 1) s1.substring s1 i i + 1 i 1 s2.substring(i, i + 1) s2.substring s2 i i + 1 i 1 {
				counter -= 1;
			} counter -= 1 counter 1 System.out.println(counter) System.out.println System.out System System.out counter String[] args args public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		
		// 文字列の入力
		String s1 = sc.next();
		String s2 = sc.next();
      int counter =  s1.length();
		for(int i = 0; i < s1.length() ; i++){
			if(s1.substring( i, i + 1).equals (s2.substring(i, i + 1))){
				counter -= 1;
			}	
		}
		// 出力
		System.out.println(counter);
	}
} public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		
		// 文字列の入力
		String s1 = sc.next();
		String s2 = sc.next();
      int counter =  s1.length();
		for(int i = 0; i < s1.length() ; i++){
			if(s1.substring( i, i + 1).equals (s2.substring(i, i + 1))){
				counter -= 1;
			}	
		}
		// 出力
		System.out.println(counter);
	}
} Main
import java.util.*;
public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		
		// 文字列の入力
		String s1 = sc.next();
		String s2 = sc.next();
      int counter =  s1.length();
		for(int i = 0; i < s1.length() ; i++){
			if(s1.substring( i, i + 1).equals (s2.substring(i, i + 1))){
				counter -= 1;
			}	
		}
		// 出力
		System.out.println(counter);
	}
}