
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();
		String[] Ss = S.split("");
		String[] Ts = T.split("");

		int count = 0;
		for(int i = 0; i < Ss.length; i++) {
			if(!Ss[i].equals(Ts[i])) {
				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);

		String S = sc.nextLine();
		String T = sc.nextLine();
		String[] Ss = S.split("");
		String[] Ts = T.split("");

		int count = 0;
		for(int i = 0; i < Ss.length; i++) {
			if(!Ss[i].equals(Ts[i])) {
				count++;
			}
		}

		System.out.println(count);
	}


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

		String S = sc.nextLine();
		String T = sc.nextLine();
		String[] Ss = S.split("");
		String[] Ts = T.split("");

		int count = 0;
		for(int i = 0; i < Ss.length; i++) {
			if(!Ss[i].equals(Ts[i])) {
				count++;
			}
		}

		System.out.println(count);
	} main {
		Scanner sc = new Scanner(System.in);

		String S = sc.nextLine();
		String T = sc.nextLine();
		String[] Ss = S.split("");
		String[] Ts = T.split("");

		int count = 0;
		for(int i = 0; i < Ss.length; i++) {
			if(!Ss[i].equals(Ts[i])) {
				count++;
			}
		}

		System.out.println(count);
	} 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 String[] Ss = S.split(""); Ss S.split("") S.split S "" String[] Ts = T.split(""); Ts T.split("") T.split T "" int count = 0; count 0 for(int i = 0; i < Ss.length; i++) {
			if(!Ss[i].equals(Ts[i])) {
				count++;
			}
		} int i = 0; int i = 0; i 0 i < Ss.length i Ss.length Ss Ss.length i++ i++ i {
			if(!Ss[i].equals(Ts[i])) {
				count++;
			}
		} {
			if(!Ss[i].equals(Ts[i])) {
				count++;
			}
		} if(!Ss[i].equals(Ts[i])) {
				count++;
			} !Ss[i].equals(Ts[i]) Ss[i].equals(Ts[i]) Ss[i].equals Ss[i] Ss i Ts[i] Ts i {
				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);

		String S = sc.nextLine();
		String T = sc.nextLine();
		String[] Ss = S.split("");
		String[] Ts = T.split("");

		int count = 0;
		for(int i = 0; i < Ss.length; i++) {
			if(!Ss[i].equals(Ts[i])) {
				count++;
			}
		}

		System.out.println(count);
	}


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

		String S = sc.nextLine();
		String T = sc.nextLine();
		String[] Ss = S.split("");
		String[] Ts = T.split("");

		int count = 0;
		for(int i = 0; i < Ss.length; i++) {
			if(!Ss[i].equals(Ts[i])) {
				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);

		String S = sc.nextLine();
		String T = sc.nextLine();
		String[] Ss = S.split("");
		String[] Ts = T.split("");

		int count = 0;
		for(int i = 0; i < Ss.length; i++) {
			if(!Ss[i].equals(Ts[i])) {
				count++;
			}
		}

		System.out.println(count);
	}


}
