import java.util.*;
import java.lang.*;
import java.io.*;
public class Main {
	public static void main(String[] args)throws java.lang.Exception
    {		
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String s=br.readLine(),t=br.readLine();
		int c=0;
		for(int i=0; i<s.length(); i++) if(s.charAt(i)!=t.charAt(i)) ++c;
		System.out.println(c);
	}
} import java.util.*; util.* java import java.lang.*; lang.* java import java.io.*; io.* java public class Main {
	public static void main(String[] args)throws java.lang.Exception
    {		
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String s=br.readLine(),t=br.readLine();
		int c=0;
		for(int i=0; i<s.length(); i++) if(s.charAt(i)!=t.charAt(i)) ++c;
		System.out.println(c);
	}
} Main public static void main(String[] args)throws java.lang.Exception
    {		
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String s=br.readLine(),t=br.readLine();
		int c=0;
		for(int i=0; i<s.length(); i++) if(s.charAt(i)!=t.charAt(i)) ++c;
		System.out.println(c);
	} main {		
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String s=br.readLine(),t=br.readLine();
		int c=0;
		for(int i=0; i<s.length(); i++) if(s.charAt(i)!=t.charAt(i)) ++c;
		System.out.println(c);
	} 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 t=br.readLine(); t br.readLine() br.readLine br int c=0; c 0 for(int i=0; i<s.length(); i++) if(s.charAt(i)!=t.charAt(i)) ++c; int i=0; int i=0; i 0 i<s.length() i s.length() s.length s i++ i++ i if(s.charAt(i)!=t.charAt(i)) ++c; if(s.charAt(i)!=t.charAt(i)) ++c; s.charAt(i)!=t.charAt(i) s.charAt(i) s.charAt s i t.charAt(i) t.charAt t i ++c c System.out.println(c) System.out.println System.out System System.out c String[] args args public class Main {
	public static void main(String[] args)throws java.lang.Exception
    {		
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String s=br.readLine(),t=br.readLine();
		int c=0;
		for(int i=0; i<s.length(); i++) if(s.charAt(i)!=t.charAt(i)) ++c;
		System.out.println(c);
	}
} public class Main {
	public static void main(String[] args)throws java.lang.Exception
    {		
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String s=br.readLine(),t=br.readLine();
		int c=0;
		for(int i=0; i<s.length(); i++) if(s.charAt(i)!=t.charAt(i)) ++c;
		System.out.println(c);
	}
} Main
import java.util.*;
import java.lang.*;
import java.io.*;
public class Main {
	public static void main(String[] args)throws java.lang.Exception
    {		
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String s=br.readLine(),t=br.readLine();
		int c=0;
		for(int i=0; i<s.length(); i++) if(s.charAt(i)!=t.charAt(i)) ++c;
		System.out.println(c);
	}
}