import java.util.Scanner;
import java.util.LinkedList;
import java.util.PriorityQueue;
import java.util.Queue;

public class Main {	
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		String s = sc.next();
		String t = sc.next();
		
		char[] S = s.toCharArray();
		char[] T = t.toCharArray();
		
		int c = 0;
		
 		for(int i = 0; i < s.length(); i++) {
 			if(S[i] != T[i]) c += 1;
		}
		
 		System.out.println(c);
	}
} import java.util.Scanner; Scanner java.util import java.util.LinkedList; LinkedList java.util import java.util.PriorityQueue; PriorityQueue java.util import java.util.Queue; Queue 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();
		
		char[] S = s.toCharArray();
		char[] T = t.toCharArray();
		
		int c = 0;
		
 		for(int i = 0; i < s.length(); i++) {
 			if(S[i] != T[i]) c += 1;
		}
		
 		System.out.println(c);
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		String s = sc.next();
		String t = sc.next();
		
		char[] S = s.toCharArray();
		char[] T = t.toCharArray();
		
		int c = 0;
		
 		for(int i = 0; i < s.length(); i++) {
 			if(S[i] != T[i]) c += 1;
		}
		
 		System.out.println(c);
	} main {
		Scanner sc = new Scanner(System.in);
		
		String s = sc.next();
		String t = sc.next();
		
		char[] S = s.toCharArray();
		char[] T = t.toCharArray();
		
		int c = 0;
		
 		for(int i = 0; i < s.length(); i++) {
 			if(S[i] != T[i]) c += 1;
		}
		
 		System.out.println(c);
	} 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 char[] S = s.toCharArray(); S s.toCharArray() s.toCharArray s char[] T = t.toCharArray(); T t.toCharArray() t.toCharArray t int c = 0; c 0 for(int i = 0; i < s.length(); i++) {
 			if(S[i] != T[i]) c += 1;
		} int i = 0; int i = 0; i 0 i < s.length() i s.length() s.length s i++ i++ i {
 			if(S[i] != T[i]) c += 1;
		} {
 			if(S[i] != T[i]) c += 1;
		} if(S[i] != T[i]) c += 1; S[i] != T[i] S[i] S i T[i] T i c += 1 c 1 System.out.println(c) System.out.println System.out System System.out c 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();
		
		char[] S = s.toCharArray();
		char[] T = t.toCharArray();
		
		int c = 0;
		
 		for(int i = 0; i < s.length(); i++) {
 			if(S[i] != T[i]) c += 1;
		}
		
 		System.out.println(c);
	}
} public class Main {	
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		String s = sc.next();
		String t = sc.next();
		
		char[] S = s.toCharArray();
		char[] T = t.toCharArray();
		
		int c = 0;
		
 		for(int i = 0; i < s.length(); i++) {
 			if(S[i] != T[i]) c += 1;
		}
		
 		System.out.println(c);
	}
} Main
import java.util.Scanner;
import java.util.LinkedList;
import java.util.PriorityQueue;
import java.util.Queue;

public class Main {	
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		String s = sc.next();
		String t = sc.next();
		
		char[] S = s.toCharArray();
		char[] T = t.toCharArray();
		
		int c = 0;
		
 		for(int i = 0; i < s.length(); i++) {
 			if(S[i] != T[i]) c += 1;
		}
		
 		System.out.println(c);
	}
}