import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String s = sc.next();
		char[] slist = new char[s.length()];
		for (int i = 0; i < s.length(); i++) {
			slist[i] = s.charAt(i);
		}
		String t = sc.next();
		char[] tlist = new char[t.length()];
		for (int i = 0; i < t.length(); i++) {
			tlist[i] = t.charAt(i);
		}

		int ans = 0;
		for (int i = 0; i < s.length(); i++) {
			if (slist[i] != tlist[i]) {
				ans++;
			}
		}

		System.out.println(ans);
		sc.close();
	}

} 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.next();
		char[] slist = new char[s.length()];
		for (int i = 0; i < s.length(); i++) {
			slist[i] = s.charAt(i);
		}
		String t = sc.next();
		char[] tlist = new char[t.length()];
		for (int i = 0; i < t.length(); i++) {
			tlist[i] = t.charAt(i);
		}

		int ans = 0;
		for (int i = 0; i < s.length(); i++) {
			if (slist[i] != tlist[i]) {
				ans++;
			}
		}

		System.out.println(ans);
		sc.close();
	}

} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String s = sc.next();
		char[] slist = new char[s.length()];
		for (int i = 0; i < s.length(); i++) {
			slist[i] = s.charAt(i);
		}
		String t = sc.next();
		char[] tlist = new char[t.length()];
		for (int i = 0; i < t.length(); i++) {
			tlist[i] = t.charAt(i);
		}

		int ans = 0;
		for (int i = 0; i < s.length(); i++) {
			if (slist[i] != tlist[i]) {
				ans++;
			}
		}

		System.out.println(ans);
		sc.close();
	} main {
		Scanner sc = new Scanner(System.in);
		String s = sc.next();
		char[] slist = new char[s.length()];
		for (int i = 0; i < s.length(); i++) {
			slist[i] = s.charAt(i);
		}
		String t = sc.next();
		char[] tlist = new char[t.length()];
		for (int i = 0; i < t.length(); i++) {
			tlist[i] = t.charAt(i);
		}

		int ans = 0;
		for (int i = 0; i < s.length(); i++) {
			if (slist[i] != tlist[i]) {
				ans++;
			}
		}

		System.out.println(ans);
		sc.close();
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String s = sc.next(); s sc.next() sc.next sc char[] slist = new char[s.length()]; slist new char[s.length()] s.length() s.length s for (int i = 0; i < s.length(); i++) {
			slist[i] = s.charAt(i);
		} int i = 0; int i = 0; i 0 i < s.length() i s.length() s.length s i++ i++ i {
			slist[i] = s.charAt(i);
		} {
			slist[i] = s.charAt(i);
		} slist[i] = s.charAt(i) slist[i] slist i s.charAt(i) s.charAt s i String t = sc.next(); t sc.next() sc.next sc char[] tlist = new char[t.length()]; tlist new char[t.length()] t.length() t.length t for (int i = 0; i < t.length(); i++) {
			tlist[i] = t.charAt(i);
		} int i = 0; int i = 0; i 0 i < t.length() i t.length() t.length t i++ i++ i {
			tlist[i] = t.charAt(i);
		} {
			tlist[i] = t.charAt(i);
		} tlist[i] = t.charAt(i) tlist[i] tlist i t.charAt(i) t.charAt t i int ans = 0; ans 0 for (int i = 0; i < s.length(); i++) {
			if (slist[i] != tlist[i]) {
				ans++;
			}
		} int i = 0; int i = 0; i 0 i < s.length() i s.length() s.length s i++ i++ i {
			if (slist[i] != tlist[i]) {
				ans++;
			}
		} {
			if (slist[i] != tlist[i]) {
				ans++;
			}
		} if (slist[i] != tlist[i]) {
				ans++;
			} slist[i] != tlist[i] slist[i] slist i tlist[i] tlist i {
				ans++;
			} ans++ ans System.out.println(ans) System.out.println System.out System System.out ans sc.close() sc.close sc String[] args args public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String s = sc.next();
		char[] slist = new char[s.length()];
		for (int i = 0; i < s.length(); i++) {
			slist[i] = s.charAt(i);
		}
		String t = sc.next();
		char[] tlist = new char[t.length()];
		for (int i = 0; i < t.length(); i++) {
			tlist[i] = t.charAt(i);
		}

		int ans = 0;
		for (int i = 0; i < s.length(); i++) {
			if (slist[i] != tlist[i]) {
				ans++;
			}
		}

		System.out.println(ans);
		sc.close();
	}

} public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String s = sc.next();
		char[] slist = new char[s.length()];
		for (int i = 0; i < s.length(); i++) {
			slist[i] = s.charAt(i);
		}
		String t = sc.next();
		char[] tlist = new char[t.length()];
		for (int i = 0; i < t.length(); i++) {
			tlist[i] = t.charAt(i);
		}

		int ans = 0;
		for (int i = 0; i < s.length(); i++) {
			if (slist[i] != tlist[i]) {
				ans++;
			}
		}

		System.out.println(ans);
		sc.close();
	}

} Main
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String s = sc.next();
		char[] slist = new char[s.length()];
		for (int i = 0; i < s.length(); i++) {
			slist[i] = s.charAt(i);
		}
		String t = sc.next();
		char[] tlist = new char[t.length()];
		for (int i = 0; i < t.length(); i++) {
			tlist[i] = t.charAt(i);
		}

		int ans = 0;
		for (int i = 0; i < s.length(); i++) {
			if (slist[i] != tlist[i]) {
				ans++;
			}
		}

		System.out.println(ans);
		sc.close();
	}

}