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

public class Main {
	public static void main (String[] args) {
		Scanner sc = new Scanner(System.in);
		char[] s = sc.next().toCharArray(); char[] t = sc.next().toCharArray();
		int count = 0; int len = s.length;
		for (int i = 0; i<len; i++) {
			if (s[i] != t[i])
				count++;
		}
		System.out.println(count);
	}
} import java.util.*; util.* java import java.io.*; io.* java import java.lang.*; lang.* java public class Main {
	public static void main (String[] args) {
		Scanner sc = new Scanner(System.in);
		char[] s = sc.next().toCharArray(); char[] t = sc.next().toCharArray();
		int count = 0; int len = s.length;
		for (int i = 0; i<len; i++) {
			if (s[i] != t[i])
				count++;
		}
		System.out.println(count);
	}
} Main public static void main (String[] args) {
		Scanner sc = new Scanner(System.in);
		char[] s = sc.next().toCharArray(); char[] t = sc.next().toCharArray();
		int count = 0; int len = s.length;
		for (int i = 0; i<len; i++) {
			if (s[i] != t[i])
				count++;
		}
		System.out.println(count);
	} main {
		Scanner sc = new Scanner(System.in);
		char[] s = sc.next().toCharArray(); char[] t = sc.next().toCharArray();
		int count = 0; int len = s.length;
		for (int i = 0; i<len; i++) {
			if (s[i] != t[i])
				count++;
		}
		System.out.println(count);
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) char[] s = sc.next().toCharArray(); s sc.next().toCharArray() sc.next().toCharArray sc.next() sc.next sc char[] t = sc.next().toCharArray(); t sc.next().toCharArray() sc.next().toCharArray sc.next() sc.next sc int count = 0; count 0 int len = s.length; len s.length s s.length for (int i = 0; i<len; i++) {
			if (s[i] != t[i])
				count++;
		} int i = 0; int i = 0; i 0 i<len i len i++ i++ i {
			if (s[i] != t[i])
				count++;
		} {
			if (s[i] != t[i])
				count++;
		} if (s[i] != t[i])
				count++; s[i] != t[i] s[i] s i t[i] t i count++ count System.out.println(count) System.out.println System.out System System.out count String[] args args public class Main {
	public static void main (String[] args) {
		Scanner sc = new Scanner(System.in);
		char[] s = sc.next().toCharArray(); char[] t = sc.next().toCharArray();
		int count = 0; int len = s.length;
		for (int i = 0; i<len; i++) {
			if (s[i] != t[i])
				count++;
		}
		System.out.println(count);
	}
} public class Main {
	public static void main (String[] args) {
		Scanner sc = new Scanner(System.in);
		char[] s = sc.next().toCharArray(); char[] t = sc.next().toCharArray();
		int count = 0; int len = s.length;
		for (int i = 0; i<len; i++) {
			if (s[i] != t[i])
				count++;
		}
		System.out.println(count);
	}
} Main
import java.util.*;
import java.io.*;
import java.lang.*;

public class Main {
	public static void main (String[] args) {
		Scanner sc = new Scanner(System.in);
		char[] s = sc.next().toCharArray(); char[] t = sc.next().toCharArray();
		int count = 0; int len = s.length;
		for (int i = 0; i<len; i++) {
			if (s[i] != t[i])
				count++;
		}
		System.out.println(count);
	}
}
