import java.io.*;

public class Main{
	private static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
	private static BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
	
	public static void main (String[] args) throws IOException{
        String s = br.readLine();
        String t = br.readLine();
        int ans = 0;
        for(int i=0;i<s.length();i++){
            if(s.charAt(i)!=t.charAt(i))    ans++;
        }
        bw.write(ans + "");
		bw.flush();
	}
} import java.io.*; io.* java public class Main{
	private static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
	private static BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
	
	public static void main (String[] args) throws IOException{
        String s = br.readLine();
        String t = br.readLine();
        int ans = 0;
        for(int i=0;i<s.length();i++){
            if(s.charAt(i)!=t.charAt(i))    ans++;
        }
        bw.write(ans + "");
		bw.flush();
	}
} Main private static BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); br new BufferedReader(new InputStreamReader(System.in)) private static BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out)); bw new BufferedWriter(new OutputStreamWriter(System.out)) public static void main (String[] args) throws IOException{
        String s = br.readLine();
        String t = br.readLine();
        int ans = 0;
        for(int i=0;i<s.length();i++){
            if(s.charAt(i)!=t.charAt(i))    ans++;
        }
        bw.write(ans + "");
		bw.flush();
	} main {
        String s = br.readLine();
        String t = br.readLine();
        int ans = 0;
        for(int i=0;i<s.length();i++){
            if(s.charAt(i)!=t.charAt(i))    ans++;
        }
        bw.write(ans + "");
		bw.flush();
	} 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 for(int i=0;i<s.length();i++){
            if(s.charAt(i)!=t.charAt(i))    ans++;
        } 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))    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 bw.write(ans + "") bw.write bw ans + "" ans "" bw.flush() bw.flush bw String[] args args public class Main{
	private static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
	private static BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
	
	public static void main (String[] args) throws IOException{
        String s = br.readLine();
        String t = br.readLine();
        int ans = 0;
        for(int i=0;i<s.length();i++){
            if(s.charAt(i)!=t.charAt(i))    ans++;
        }
        bw.write(ans + "");
		bw.flush();
	}
} public class Main{
	private static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
	private static BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
	
	public static void main (String[] args) throws IOException{
        String s = br.readLine();
        String t = br.readLine();
        int ans = 0;
        for(int i=0;i<s.length();i++){
            if(s.charAt(i)!=t.charAt(i))    ans++;
        }
        bw.write(ans + "");
		bw.flush();
	}
} Main
import java.io.*;

public class Main{
	private static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
	private static BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
	
	public static void main (String[] args) throws IOException{
        String s = br.readLine();
        String t = br.readLine();
        int ans = 0;
        for(int i=0;i<s.length();i++){
            if(s.charAt(i)!=t.charAt(i))    ans++;
        }
        bw.write(ans + "");
		bw.flush();
	}
}
