import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		String S = sc.nextLine();
		String T = sc.nextLine();
		char[] s = new char[S.length()];
		char[] t = new char[T.length()];
		int a = 0;

		for(int i = 0;i<S.length();i++) {
			s[i] = S.charAt(i);
			t[i] = T.charAt(i);
			if(s[i]!=t[i]) {
				a++;
			}
		}
		System.out.println(a);
	}

} import java.util.Scanner; Scanner java.util public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		String S = sc.nextLine();
		String T = sc.nextLine();
		char[] s = new char[S.length()];
		char[] t = new char[T.length()];
		int a = 0;

		for(int i = 0;i<S.length();i++) {
			s[i] = S.charAt(i);
			t[i] = T.charAt(i);
			if(s[i]!=t[i]) {
				a++;
			}
		}
		System.out.println(a);
	}

} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		String S = sc.nextLine();
		String T = sc.nextLine();
		char[] s = new char[S.length()];
		char[] t = new char[T.length()];
		int a = 0;

		for(int i = 0;i<S.length();i++) {
			s[i] = S.charAt(i);
			t[i] = T.charAt(i);
			if(s[i]!=t[i]) {
				a++;
			}
		}
		System.out.println(a);
	} main {
		Scanner sc = new Scanner(System.in);

		String S = sc.nextLine();
		String T = sc.nextLine();
		char[] s = new char[S.length()];
		char[] t = new char[T.length()];
		int a = 0;

		for(int i = 0;i<S.length();i++) {
			s[i] = S.charAt(i);
			t[i] = T.charAt(i);
			if(s[i]!=t[i]) {
				a++;
			}
		}
		System.out.println(a);
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String S = sc.nextLine(); S sc.nextLine() sc.nextLine sc String T = sc.nextLine(); T sc.nextLine() sc.nextLine sc char[] s = new char[S.length()]; s new char[S.length()] S.length() S.length S char[] t = new char[T.length()]; t new char[T.length()] T.length() T.length T int a = 0; a 0 for(int i = 0;i<S.length();i++) {
			s[i] = S.charAt(i);
			t[i] = T.charAt(i);
			if(s[i]!=t[i]) {
				a++;
			}
		} int i = 0; int i = 0; i 0 i<S.length() i S.length() S.length S i++ i++ i {
			s[i] = S.charAt(i);
			t[i] = T.charAt(i);
			if(s[i]!=t[i]) {
				a++;
			}
		} {
			s[i] = S.charAt(i);
			t[i] = T.charAt(i);
			if(s[i]!=t[i]) {
				a++;
			}
		} s[i] = S.charAt(i) s[i] s i S.charAt(i) S.charAt S i t[i] = T.charAt(i) t[i] t i T.charAt(i) T.charAt T i if(s[i]!=t[i]) {
				a++;
			} s[i]!=t[i] s[i] s i t[i] t i {
				a++;
			} a++ a System.out.println(a) System.out.println System.out System System.out a String[] args args public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		String S = sc.nextLine();
		String T = sc.nextLine();
		char[] s = new char[S.length()];
		char[] t = new char[T.length()];
		int a = 0;

		for(int i = 0;i<S.length();i++) {
			s[i] = S.charAt(i);
			t[i] = T.charAt(i);
			if(s[i]!=t[i]) {
				a++;
			}
		}
		System.out.println(a);
	}

} public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		String S = sc.nextLine();
		String T = sc.nextLine();
		char[] s = new char[S.length()];
		char[] t = new char[T.length()];
		int a = 0;

		for(int i = 0;i<S.length();i++) {
			s[i] = S.charAt(i);
			t[i] = T.charAt(i);
			if(s[i]!=t[i]) {
				a++;
			}
		}
		System.out.println(a);
	}

} Main
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		String S = sc.nextLine();
		String T = sc.nextLine();
		char[] s = new char[S.length()];
		char[] t = new char[T.length()];
		int a = 0;

		for(int i = 0;i<S.length();i++) {
			s[i] = S.charAt(i);
			t[i] = T.charAt(i);
			if(s[i]!=t[i]) {
				a++;
			}
		}
		System.out.println(a);
	}

}
