import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		String s = scan.next();
		String t = scan.next();
		char[] S = s.toCharArray();
		char[] T = t.toCharArray();
		int count = 0;

		for(int i = 0;i < s.length();i++) {
			if(S[i] != T[i]) {
				count += 1;
			}
		}

		System.out.println(count);
	}
} import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		String s = scan.next();
		String t = scan.next();
		char[] S = s.toCharArray();
		char[] T = t.toCharArray();
		int count = 0;

		for(int i = 0;i < s.length();i++) {
			if(S[i] != T[i]) {
				count += 1;
			}
		}

		System.out.println(count);
	}
} Main public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		String s = scan.next();
		String t = scan.next();
		char[] S = s.toCharArray();
		char[] T = t.toCharArray();
		int count = 0;

		for(int i = 0;i < s.length();i++) {
			if(S[i] != T[i]) {
				count += 1;
			}
		}

		System.out.println(count);
	} main {
		Scanner scan = new Scanner(System.in);
		String s = scan.next();
		String t = scan.next();
		char[] S = s.toCharArray();
		char[] T = t.toCharArray();
		int count = 0;

		for(int i = 0;i < s.length();i++) {
			if(S[i] != T[i]) {
				count += 1;
			}
		}

		System.out.println(count);
	} Scanner scan = new Scanner(System.in); scan new Scanner(System.in) String s = scan.next(); s scan.next() scan.next scan String t = scan.next(); t scan.next() scan.next scan char[] S = s.toCharArray(); S s.toCharArray() s.toCharArray s char[] T = t.toCharArray(); T t.toCharArray() t.toCharArray t int count = 0; count 0 for(int i = 0;i < s.length();i++) {
			if(S[i] != T[i]) {
				count += 1;
			}
		} int i = 0; int i = 0; i 0 i < s.length() i s.length() s.length s i++ i++ i {
			if(S[i] != T[i]) {
				count += 1;
			}
		} {
			if(S[i] != T[i]) {
				count += 1;
			}
		} if(S[i] != T[i]) {
				count += 1;
			} S[i] != T[i] S[i] S i T[i] T i {
				count += 1;
			} count += 1 count 1 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 scan = new Scanner(System.in);
		String s = scan.next();
		String t = scan.next();
		char[] S = s.toCharArray();
		char[] T = t.toCharArray();
		int count = 0;

		for(int i = 0;i < s.length();i++) {
			if(S[i] != T[i]) {
				count += 1;
			}
		}

		System.out.println(count);
	}
} public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		String s = scan.next();
		String t = scan.next();
		char[] S = s.toCharArray();
		char[] T = t.toCharArray();
		int count = 0;

		for(int i = 0;i < s.length();i++) {
			if(S[i] != T[i]) {
				count += 1;
			}
		}

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

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		String s = scan.next();
		String t = scan.next();
		char[] S = s.toCharArray();
		char[] T = t.toCharArray();
		int count = 0;

		for(int i = 0;i < s.length();i++) {
			if(S[i] != T[i]) {
				count += 1;
			}
		}

		System.out.println(count);
	}
}
