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();	
			
		String[] strArrayS = S.split("");
		String[] strArrayT = T.split("");
		
		int Slong = S.length();
		
		int count = 0;
		for (int i=0; i<Slong; i++) {
			if(!strArrayS[i].contentEquals(strArrayT[i])) {

				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();	
			
		String[] strArrayS = S.split("");
		String[] strArrayT = T.split("");
		
		int Slong = S.length();
		
		int count = 0;
		for (int i=0; i<Slong; i++) {
			if(!strArrayS[i].contentEquals(strArrayT[i])) {

				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();	
			
		String[] strArrayS = S.split("");
		String[] strArrayT = T.split("");
		
		int Slong = S.length();
		
		int count = 0;
		for (int i=0; i<Slong; i++) {
			if(!strArrayS[i].contentEquals(strArrayT[i])) {

				count++;
			}
		}
					
							
		System.out.println(count);
		keyboard.close();	
	} main {
		
		Scanner keyboard = new Scanner(System.in); 
		
		String S = keyboard.next();	
		String T = keyboard.next();	
			
		String[] strArrayS = S.split("");
		String[] strArrayT = T.split("");
		
		int Slong = S.length();
		
		int count = 0;
		for (int i=0; i<Slong; i++) {
			if(!strArrayS[i].contentEquals(strArrayT[i])) {

				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 String[] strArrayS = S.split(""); strArrayS S.split("") S.split S "" String[] strArrayT = T.split(""); strArrayT T.split("") T.split T "" int Slong = S.length(); Slong S.length() S.length S int count = 0; count 0 for (int i=0; i<Slong; i++) {
			if(!strArrayS[i].contentEquals(strArrayT[i])) {

				count++;
			}
		} int i=0; int i=0; i 0 i<Slong i Slong i++ i++ i {
			if(!strArrayS[i].contentEquals(strArrayT[i])) {

				count++;
			}
		} {
			if(!strArrayS[i].contentEquals(strArrayT[i])) {

				count++;
			}
		} if(!strArrayS[i].contentEquals(strArrayT[i])) {

				count++;
			} !strArrayS[i].contentEquals(strArrayT[i]) strArrayS[i].contentEquals(strArrayT[i]) strArrayS[i].contentEquals strArrayS[i] strArrayS i strArrayT[i] strArrayT 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();	
			
		String[] strArrayS = S.split("");
		String[] strArrayT = T.split("");
		
		int Slong = S.length();
		
		int count = 0;
		for (int i=0; i<Slong; i++) {
			if(!strArrayS[i].contentEquals(strArrayT[i])) {

				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();	
			
		String[] strArrayS = S.split("");
		String[] strArrayT = T.split("");
		
		int Slong = S.length();
		
		int count = 0;
		for (int i=0; i<Slong; i++) {
			if(!strArrayS[i].contentEquals(strArrayT[i])) {

				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();	
			
		String[] strArrayS = S.split("");
		String[] strArrayT = T.split("");
		
		int Slong = S.length();
		
		int count = 0;
		for (int i=0; i<Slong; i++) {
			if(!strArrayS[i].contentEquals(strArrayT[i])) {

				count++;
			}
		}
					
							
		System.out.println(count);
		keyboard.close();	
	}
}
