import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		char[] l1 = sc.nextLine().toCharArray();
		char[] l2 = sc.nextLine().toCharArray();

		int count = 0;
		for (int id = 0; id < l1.length; id++) {
			if (l1[id] != l2[id]) {
				count++;
			}
		}

		System.out.println(count);
	}
} import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		char[] l1 = sc.nextLine().toCharArray();
		char[] l2 = sc.nextLine().toCharArray();

		int count = 0;
		for (int id = 0; id < l1.length; id++) {
			if (l1[id] != l2[id]) {
				count++;
			}
		}

		System.out.println(count);
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		char[] l1 = sc.nextLine().toCharArray();
		char[] l2 = sc.nextLine().toCharArray();

		int count = 0;
		for (int id = 0; id < l1.length; id++) {
			if (l1[id] != l2[id]) {
				count++;
			}
		}

		System.out.println(count);
	} main {
		Scanner sc = new Scanner(System.in);
		char[] l1 = sc.nextLine().toCharArray();
		char[] l2 = sc.nextLine().toCharArray();

		int count = 0;
		for (int id = 0; id < l1.length; id++) {
			if (l1[id] != l2[id]) {
				count++;
			}
		}

		System.out.println(count);
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) char[] l1 = sc.nextLine().toCharArray(); l1 sc.nextLine().toCharArray() sc.nextLine().toCharArray sc.nextLine() sc.nextLine sc char[] l2 = sc.nextLine().toCharArray(); l2 sc.nextLine().toCharArray() sc.nextLine().toCharArray sc.nextLine() sc.nextLine sc int count = 0; count 0 for (int id = 0; id < l1.length; id++) {
			if (l1[id] != l2[id]) {
				count++;
			}
		} int id = 0; int id = 0; id 0 id < l1.length id l1.length l1 l1.length id++ id++ id {
			if (l1[id] != l2[id]) {
				count++;
			}
		} {
			if (l1[id] != l2[id]) {
				count++;
			}
		} if (l1[id] != l2[id]) {
				count++;
			} l1[id] != l2[id] l1[id] l1 id l2[id] l2 id {
				count++;
			} 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[] l1 = sc.nextLine().toCharArray();
		char[] l2 = sc.nextLine().toCharArray();

		int count = 0;
		for (int id = 0; id < l1.length; id++) {
			if (l1[id] != l2[id]) {
				count++;
			}
		}

		System.out.println(count);
	}
} public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		char[] l1 = sc.nextLine().toCharArray();
		char[] l2 = sc.nextLine().toCharArray();

		int count = 0;
		for (int id = 0; id < l1.length; id++) {
			if (l1[id] != l2[id]) {
				count++;
			}
		}

		System.out.println(count);
	}
} Main
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		char[] l1 = sc.nextLine().toCharArray();
		char[] l2 = sc.nextLine().toCharArray();

		int count = 0;
		for (int id = 0; id < l1.length; id++) {
			if (l1[id] != l2[id]) {
				count++;
			}
		}

		System.out.println(count);
	}
}
