import java.util.*;
import java.io.*;
public class Main{
	public static void main(String[] args) throws IOException{
		BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
	char[] list1 = reader.readLine().toCharArray();
	char[] list2 = reader.readLine().toCharArray();
	long res = 0;
	for(int i = 0;i<list1.length;i++){
		if(list1[i]!=list2[i]) res++;
	}
	System.out.println(res);
	}
} import java.util.*; util.* java import java.io.*; io.* java public class Main{
	public static void main(String[] args) throws IOException{
		BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
	char[] list1 = reader.readLine().toCharArray();
	char[] list2 = reader.readLine().toCharArray();
	long res = 0;
	for(int i = 0;i<list1.length;i++){
		if(list1[i]!=list2[i]) res++;
	}
	System.out.println(res);
	}
} Main public static void main(String[] args) throws IOException{
		BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
	char[] list1 = reader.readLine().toCharArray();
	char[] list2 = reader.readLine().toCharArray();
	long res = 0;
	for(int i = 0;i<list1.length;i++){
		if(list1[i]!=list2[i]) res++;
	}
	System.out.println(res);
	} main {
		BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
	char[] list1 = reader.readLine().toCharArray();
	char[] list2 = reader.readLine().toCharArray();
	long res = 0;
	for(int i = 0;i<list1.length;i++){
		if(list1[i]!=list2[i]) res++;
	}
	System.out.println(res);
	} BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); reader new BufferedReader(new InputStreamReader(System.in)) char[] list1 = reader.readLine().toCharArray(); list1 reader.readLine().toCharArray() reader.readLine().toCharArray reader.readLine() reader.readLine reader char[] list2 = reader.readLine().toCharArray(); list2 reader.readLine().toCharArray() reader.readLine().toCharArray reader.readLine() reader.readLine reader long res = 0; res 0 for(int i = 0;i<list1.length;i++){
		if(list1[i]!=list2[i]) res++;
	} int i = 0; int i = 0; i 0 i<list1.length i list1.length list1 list1.length i++ i++ i {
		if(list1[i]!=list2[i]) res++;
	} {
		if(list1[i]!=list2[i]) res++;
	} if(list1[i]!=list2[i]) res++; list1[i]!=list2[i] list1[i] list1 i list2[i] list2 i res++ res System.out.println(res) System.out.println System.out System System.out res String[] args args public class Main{
	public static void main(String[] args) throws IOException{
		BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
	char[] list1 = reader.readLine().toCharArray();
	char[] list2 = reader.readLine().toCharArray();
	long res = 0;
	for(int i = 0;i<list1.length;i++){
		if(list1[i]!=list2[i]) res++;
	}
	System.out.println(res);
	}
} public class Main{
	public static void main(String[] args) throws IOException{
		BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
	char[] list1 = reader.readLine().toCharArray();
	char[] list2 = reader.readLine().toCharArray();
	long res = 0;
	for(int i = 0;i<list1.length;i++){
		if(list1[i]!=list2[i]) res++;
	}
	System.out.println(res);
	}
} Main
import java.util.*;
import java.io.*;
public class Main{
	public static void main(String[] args) throws IOException{
		BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
	char[] list1 = reader.readLine().toCharArray();
	char[] list2 = reader.readLine().toCharArray();
	long res = 0;
	for(int i = 0;i<list1.length;i++){
		if(list1[i]!=list2[i]) res++;
	}
	System.out.println(res);
	}
}
