
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();
		int s = S.length();
		int ans = 0;

	    for(int i = 0;i<S.length();i++) {
	    	if(!((S.charAt(i)==(T.charAt(i))))){
	    		ans ++;
	    	}
	    }
	    System.out.println(ans);

	}

} 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();
		int s = S.length();
		int ans = 0;

	    for(int i = 0;i<S.length();i++) {
	    	if(!((S.charAt(i)==(T.charAt(i))))){
	    		ans ++;
	    	}
	    }
	    System.out.println(ans);

	}

} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String S = sc.nextLine();
		String T = sc.nextLine();
		int s = S.length();
		int ans = 0;

	    for(int i = 0;i<S.length();i++) {
	    	if(!((S.charAt(i)==(T.charAt(i))))){
	    		ans ++;
	    	}
	    }
	    System.out.println(ans);

	} main {
		Scanner sc = new Scanner(System.in);
		String S = sc.nextLine();
		String T = sc.nextLine();
		int s = S.length();
		int ans = 0;

	    for(int i = 0;i<S.length();i++) {
	    	if(!((S.charAt(i)==(T.charAt(i))))){
	    		ans ++;
	    	}
	    }
	    System.out.println(ans);

	} 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 int s = S.length(); s S.length() S.length S 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)==(T.charAt(i)))) S.charAt(i) S.charAt S i (T.charAt(i)) T.charAt T i {
	    		ans ++;
	    	} ans ++ ans System.out.println(ans) System.out.println System.out System System.out ans 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();
		int s = S.length();
		int ans = 0;

	    for(int i = 0;i<S.length();i++) {
	    	if(!((S.charAt(i)==(T.charAt(i))))){
	    		ans ++;
	    	}
	    }
	    System.out.println(ans);

	}

} public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String S = sc.nextLine();
		String T = sc.nextLine();
		int s = S.length();
		int ans = 0;

	    for(int i = 0;i<S.length();i++) {
	    	if(!((S.charAt(i)==(T.charAt(i))))){
	    		ans ++;
	    	}
	    }
	    System.out.println(ans);

	}

} 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();
		int s = S.length();
		int ans = 0;

	    for(int i = 0;i<S.length();i++) {
	    	if(!((S.charAt(i)==(T.charAt(i))))){
	    		ans ++;
	    	}
	    }
	    System.out.println(ans);

	}

}
