

import java.util.Scanner;

public class Main {
	public static void main(String[] args){
		int count = 0;
		int length = 0;
		Scanner sc = new Scanner(System.in);
			String s = sc.next();
			length = s.length();
			String t = sc.next();		
			
			if(t.length() != length) {
				System.out.println("2 String have diffrent length.");
				return;
			}	
			
			for(int i=0;i<length;i++) {
				if(!s.substring(i, i+1).equals(t.substring(i,i+1))){
					count++;
				}
			}
			System.out.println(count);
			count=0;
		
	}
	
} import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args){
		int count = 0;
		int length = 0;
		Scanner sc = new Scanner(System.in);
			String s = sc.next();
			length = s.length();
			String t = sc.next();		
			
			if(t.length() != length) {
				System.out.println("2 String have diffrent length.");
				return;
			}	
			
			for(int i=0;i<length;i++) {
				if(!s.substring(i, i+1).equals(t.substring(i,i+1))){
					count++;
				}
			}
			System.out.println(count);
			count=0;
		
	}
	
} Main public static void main(String[] args){
		int count = 0;
		int length = 0;
		Scanner sc = new Scanner(System.in);
			String s = sc.next();
			length = s.length();
			String t = sc.next();		
			
			if(t.length() != length) {
				System.out.println("2 String have diffrent length.");
				return;
			}	
			
			for(int i=0;i<length;i++) {
				if(!s.substring(i, i+1).equals(t.substring(i,i+1))){
					count++;
				}
			}
			System.out.println(count);
			count=0;
		
	} main {
		int count = 0;
		int length = 0;
		Scanner sc = new Scanner(System.in);
			String s = sc.next();
			length = s.length();
			String t = sc.next();		
			
			if(t.length() != length) {
				System.out.println("2 String have diffrent length.");
				return;
			}	
			
			for(int i=0;i<length;i++) {
				if(!s.substring(i, i+1).equals(t.substring(i,i+1))){
					count++;
				}
			}
			System.out.println(count);
			count=0;
		
	} int count = 0; count 0 int length = 0; length 0 Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String s = sc.next(); s sc.next() sc.next sc length = s.length() length s.length() s.length s String t = sc.next(); t sc.next() sc.next sc if(t.length() != length) {
				System.out.println("2 String have diffrent length.");
				return;
			} t.length() != length t.length() t.length t length {
				System.out.println("2 String have diffrent length.");
				return;
			} System.out.println("2 String have diffrent length.") System.out.println System.out System System.out "2 String have diffrent length." return; for(int i=0;i<length;i++) {
				if(!s.substring(i, i+1).equals(t.substring(i,i+1))){
					count++;
				}
			} int i=0; int i=0; i 0 i<length i length i++ i++ i {
				if(!s.substring(i, i+1).equals(t.substring(i,i+1))){
					count++;
				}
			} {
				if(!s.substring(i, i+1).equals(t.substring(i,i+1))){
					count++;
				}
			} if(!s.substring(i, i+1).equals(t.substring(i,i+1))){
					count++;
				} !s.substring(i, i+1).equals(t.substring(i,i+1)) s.substring(i, i+1).equals(t.substring(i,i+1)) s.substring(i, i+1).equals s.substring(i, i+1) s.substring s i i+1 i 1 t.substring(i,i+1) t.substring t i i+1 i 1 {
					count++;
				} count++ count System.out.println(count) System.out.println System.out System System.out count count=0 count 0 String[] args args public class Main {
	public static void main(String[] args){
		int count = 0;
		int length = 0;
		Scanner sc = new Scanner(System.in);
			String s = sc.next();
			length = s.length();
			String t = sc.next();		
			
			if(t.length() != length) {
				System.out.println("2 String have diffrent length.");
				return;
			}	
			
			for(int i=0;i<length;i++) {
				if(!s.substring(i, i+1).equals(t.substring(i,i+1))){
					count++;
				}
			}
			System.out.println(count);
			count=0;
		
	}
	
} public class Main {
	public static void main(String[] args){
		int count = 0;
		int length = 0;
		Scanner sc = new Scanner(System.in);
			String s = sc.next();
			length = s.length();
			String t = sc.next();		
			
			if(t.length() != length) {
				System.out.println("2 String have diffrent length.");
				return;
			}	
			
			for(int i=0;i<length;i++) {
				if(!s.substring(i, i+1).equals(t.substring(i,i+1))){
					count++;
				}
			}
			System.out.println(count);
			count=0;
		
	}
	
} Main


import java.util.Scanner;

public class Main {
	public static void main(String[] args){
		int count = 0;
		int length = 0;
		Scanner sc = new Scanner(System.in);
			String s = sc.next();
			length = s.length();
			String t = sc.next();		
			
			if(t.length() != length) {
				System.out.println("2 String have diffrent length.");
				return;
			}	
			
			for(int i=0;i<length;i++) {
				if(!s.substring(i, i+1).equals(t.substring(i,i+1))){
					count++;
				}
			}
			System.out.println(count);
			count=0;
		
	}
	
}