

import java.util.*;

public class Main {
public static void main(String[] args) {
		
		Scanner keyboard = new Scanner(System.in); 
		
		String S = keyboard.next();	
		String T = keyboard.next();	
		
		int Slong = S.length();
		
		int count = 0;
		for (int i=0; i<Slong; i++) {
			if(S.charAt(i) == T.charAt(i)) {
				
			}else {
				count++;
			}
		}
					
							
		System.out.println(count);
		keyboard.close();	
	}
}



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


import java.util.*;

public class Main {
public static void main(String[] args) {
		
		Scanner keyboard = new Scanner(System.in); 
		
		String S = keyboard.next();	
		String T = keyboard.next();	
		
		int Slong = S.length();
		
		int count = 0;
		for (int i=0; i<Slong; i++) {
			if(S.charAt(i) == T.charAt(i)) {
				
			}else {
				count++;
			}
		}
					
							
		System.out.println(count);
		keyboard.close();	
	}
}




