import java.util.*;
import java.io.*;
import java.lang.*;
public class Main {

	public static void main(String[] args) throws Exception{
		// TODO Auto-generated method stub
		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		String s1=br.readLine().trim();
		String s2=br.readLine().trim();
		int count=0;
		for(int i=0;i<s1.length();i++)
			if(s1.charAt(i)!=s2.charAt(i))
				count++;
		System.out.println(count);
	}

} import java.util.*; util.* java import java.io.*; io.* java import java.lang.*; lang.* java public class Main {

	public static void main(String[] args) throws Exception{
		// TODO Auto-generated method stub
		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		String s1=br.readLine().trim();
		String s2=br.readLine().trim();
		int count=0;
		for(int i=0;i<s1.length();i++)
			if(s1.charAt(i)!=s2.charAt(i))
				count++;
		System.out.println(count);
	}

} Main public static void main(String[] args) throws Exception{
		// TODO Auto-generated method stub
		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		String s1=br.readLine().trim();
		String s2=br.readLine().trim();
		int count=0;
		for(int i=0;i<s1.length();i++)
			if(s1.charAt(i)!=s2.charAt(i))
				count++;
		System.out.println(count);
	} main {
		// TODO Auto-generated method stub
		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		String s1=br.readLine().trim();
		String s2=br.readLine().trim();
		int count=0;
		for(int i=0;i<s1.length();i++)
			if(s1.charAt(i)!=s2.charAt(i))
				count++;
		System.out.println(count);
	} BufferedReader br=new BufferedReader(new InputStreamReader(System.in)); br new BufferedReader(new InputStreamReader(System.in)) String s1=br.readLine().trim(); s1 br.readLine().trim() br.readLine().trim br.readLine() br.readLine br String s2=br.readLine().trim(); s2 br.readLine().trim() br.readLine().trim br.readLine() br.readLine br int count=0; count 0 for(int i=0;i<s1.length();i++)
			if(s1.charAt(i)!=s2.charAt(i))
				count++; int i=0; int i=0; i 0 i<s1.length() i s1.length() s1.length s1 i++ i++ i if(s1.charAt(i)!=s2.charAt(i))
				count++; if(s1.charAt(i)!=s2.charAt(i))
				count++; s1.charAt(i)!=s2.charAt(i) s1.charAt(i) s1.charAt s1 i s2.charAt(i) s2.charAt s2 i count++ count System.out.println(count) System.out.println System.out System System.out count String[] args args public class Main {

	public static void main(String[] args) throws Exception{
		// TODO Auto-generated method stub
		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		String s1=br.readLine().trim();
		String s2=br.readLine().trim();
		int count=0;
		for(int i=0;i<s1.length();i++)
			if(s1.charAt(i)!=s2.charAt(i))
				count++;
		System.out.println(count);
	}

} public class Main {

	public static void main(String[] args) throws Exception{
		// TODO Auto-generated method stub
		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		String s1=br.readLine().trim();
		String s2=br.readLine().trim();
		int count=0;
		for(int i=0;i<s1.length();i++)
			if(s1.charAt(i)!=s2.charAt(i))
				count++;
		System.out.println(count);
	}

} Main
import java.util.*;
import java.io.*;
import java.lang.*;
public class Main {

	public static void main(String[] args) throws Exception{
		// TODO Auto-generated method stub
		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		String s1=br.readLine().trim();
		String s2=br.readLine().trim();
		int count=0;
		for(int i=0;i<s1.length();i++)
			if(s1.charAt(i)!=s2.charAt(i))
				count++;
		System.out.println(count);
	}

}
