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

public class Main {
    public static void main(String[] args) throws Exception {

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

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        PrintWriter out = new PrintWriter(new OutputStreamWriter(System.out));
        
        String s = br.readLine();
        String t = br.readLine();
        int count = 0;
        
        for(int i = 0; i < s.length(); i++){
            if(s.charAt(i) != t.charAt(i)){
                count++;
            }
        }
        
        out.println(count);
        out.close();
        
    }
} Main public static void main(String[] args) throws Exception {

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        PrintWriter out = new PrintWriter(new OutputStreamWriter(System.out));
        
        String s = br.readLine();
        String t = br.readLine();
        int count = 0;
        
        for(int i = 0; i < s.length(); i++){
            if(s.charAt(i) != t.charAt(i)){
                count++;
            }
        }
        
        out.println(count);
        out.close();
        
    } main {

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        PrintWriter out = new PrintWriter(new OutputStreamWriter(System.out));
        
        String s = br.readLine();
        String t = br.readLine();
        int count = 0;
        
        for(int i = 0; i < s.length(); i++){
            if(s.charAt(i) != t.charAt(i)){
                count++;
            }
        }
        
        out.println(count);
        out.close();
        
    } BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); br new BufferedReader(new InputStreamReader(System.in)) PrintWriter out = new PrintWriter(new OutputStreamWriter(System.out)); out new PrintWriter(new OutputStreamWriter(System.out)) String s = br.readLine(); s br.readLine() br.readLine br String t = br.readLine(); t br.readLine() br.readLine br int count = 0; count 0 for(int i = 0; i < s.length(); i++){
            if(s.charAt(i) != t.charAt(i)){
                count++;
            }
        } 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)){
                count++;
            }
        } {
            if(s.charAt(i) != t.charAt(i)){
                count++;
            }
        } if(s.charAt(i) != t.charAt(i)){
                count++;
            } s.charAt(i) != t.charAt(i) s.charAt(i) s.charAt s i t.charAt(i) t.charAt t i {
                count++;
            } count++ count out.println(count) out.println out count out.close() out.close out String[] args args public class Main {
    public static void main(String[] args) throws Exception {

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        PrintWriter out = new PrintWriter(new OutputStreamWriter(System.out));
        
        String s = br.readLine();
        String t = br.readLine();
        int count = 0;
        
        for(int i = 0; i < s.length(); i++){
            if(s.charAt(i) != t.charAt(i)){
                count++;
            }
        }
        
        out.println(count);
        out.close();
        
    }
} public class Main {
    public static void main(String[] args) throws Exception {

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        PrintWriter out = new PrintWriter(new OutputStreamWriter(System.out));
        
        String s = br.readLine();
        String t = br.readLine();
        int count = 0;
        
        for(int i = 0; i < s.length(); i++){
            if(s.charAt(i) != t.charAt(i)){
                count++;
            }
        }
        
        out.println(count);
        out.close();
        
    }
} Main
import java.util.*;
import java.io.*;

public class Main {
    public static void main(String[] args) throws Exception {

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        PrintWriter out = new PrintWriter(new OutputStreamWriter(System.out));
        
        String s = br.readLine();
        String t = br.readLine();
        int count = 0;
        
        for(int i = 0; i < s.length(); i++){
            if(s.charAt(i) != t.charAt(i)){
                count++;
            }
        }
        
        out.println(count);
        out.close();
        
    }
}