import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;

public class Main {

	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
		
		String s = br.readLine();
		String t = br.readLine();
		
		char[] chs = s.toCharArray();
		char[] cht = t.toCharArray(); 
		int cnt = 0;
		for(int i=0; i<s.length(); i++) {
			if(chs[i] != cht[i])
				cnt++;
		}
		
		bw.write(cnt + "\n");
		bw.flush();
	}

} import java.io.BufferedReader; BufferedReader java.io import java.io.BufferedWriter; BufferedWriter java.io import java.io.IOException; IOException java.io import java.io.InputStreamReader; InputStreamReader java.io import java.io.OutputStreamWriter; OutputStreamWriter java.io public class Main {

	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
		
		String s = br.readLine();
		String t = br.readLine();
		
		char[] chs = s.toCharArray();
		char[] cht = t.toCharArray(); 
		int cnt = 0;
		for(int i=0; i<s.length(); i++) {
			if(chs[i] != cht[i])
				cnt++;
		}
		
		bw.write(cnt + "\n");
		bw.flush();
	}

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

	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
		
		String s = br.readLine();
		String t = br.readLine();
		
		char[] chs = s.toCharArray();
		char[] cht = t.toCharArray(); 
		int cnt = 0;
		for(int i=0; i<s.length(); i++) {
			if(chs[i] != cht[i])
				cnt++;
		}
		
		bw.write(cnt + "\n");
		bw.flush();
	}

} public class Main {

	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
		
		String s = br.readLine();
		String t = br.readLine();
		
		char[] chs = s.toCharArray();
		char[] cht = t.toCharArray(); 
		int cnt = 0;
		for(int i=0; i<s.length(); i++) {
			if(chs[i] != cht[i])
				cnt++;
		}
		
		bw.write(cnt + "\n");
		bw.flush();
	}

} Main
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;

public class Main {

	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
		
		String s = br.readLine();
		String t = br.readLine();
		
		char[] chs = s.toCharArray();
		char[] cht = t.toCharArray(); 
		int cnt = 0;
		for(int i=0; i<s.length(); i++) {
			if(chs[i] != cht[i])
				cnt++;
		}
		
		bw.write(cnt + "\n");
		bw.flush();
	}

}
