
import java.util.*;
import java.io.*;

public class Main{
	public static void main(String[] args) throws IOException {
		// TODO Auto-generated method stub
		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		String s=br.readLine();
		String t=br.readLine();
		int ans=0;
		int n=s.length();
		for(int i=0;i<n;i++)
		{
			if(s.charAt(i)!=t.charAt(i))
			ans++;
		}
		System.out.println(ans);
	}
} import java.util.*; util.* java import java.io.*; io.* java public class Main{
	public static void main(String[] args) throws IOException {
		// TODO Auto-generated method stub
		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		String s=br.readLine();
		String t=br.readLine();
		int ans=0;
		int n=s.length();
		for(int i=0;i<n;i++)
		{
			if(s.charAt(i)!=t.charAt(i))
			ans++;
		}
		System.out.println(ans);
	}
} Main public static void main(String[] args) throws IOException {
		// TODO Auto-generated method stub
		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		String s=br.readLine();
		String t=br.readLine();
		int ans=0;
		int n=s.length();
		for(int i=0;i<n;i++)
		{
			if(s.charAt(i)!=t.charAt(i))
			ans++;
		}
		System.out.println(ans);
	} main {
		// TODO Auto-generated method stub
		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		String s=br.readLine();
		String t=br.readLine();
		int ans=0;
		int n=s.length();
		for(int i=0;i<n;i++)
		{
			if(s.charAt(i)!=t.charAt(i))
			ans++;
		}
		System.out.println(ans);
	} BufferedReader br=new BufferedReader(new InputStreamReader(System.in)); br new BufferedReader(new InputStreamReader(System.in)) String s=br.readLine(); s br.readLine() br.readLine br String t=br.readLine(); t br.readLine() br.readLine br int ans=0; ans 0 int n=s.length(); n s.length() s.length s for(int i=0;i<n;i++)
		{
			if(s.charAt(i)!=t.charAt(i))
			ans++;
		} int i=0; int i=0; i 0 i<n i n i++ i++ i {
			if(s.charAt(i)!=t.charAt(i))
			ans++;
		} {
			if(s.charAt(i)!=t.charAt(i))
			ans++;
		} if(s.charAt(i)!=t.charAt(i))
			ans++; s.charAt(i)!=t.charAt(i) s.charAt(i) s.charAt s i t.charAt(i) t.charAt t i ans++ ans System.out.println(ans) System.out.println System.out System System.out ans String[] args args public class Main{
	public static void main(String[] args) throws IOException {
		// TODO Auto-generated method stub
		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		String s=br.readLine();
		String t=br.readLine();
		int ans=0;
		int n=s.length();
		for(int i=0;i<n;i++)
		{
			if(s.charAt(i)!=t.charAt(i))
			ans++;
		}
		System.out.println(ans);
	}
} public class Main{
	public static void main(String[] args) throws IOException {
		// TODO Auto-generated method stub
		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		String s=br.readLine();
		String t=br.readLine();
		int ans=0;
		int n=s.length();
		for(int i=0;i<n;i++)
		{
			if(s.charAt(i)!=t.charAt(i))
			ans++;
		}
		System.out.println(ans);
	}
} Main

import java.util.*;
import java.io.*;

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