

import java.io.BufferedReader;
import java.io.InputStreamReader;

public class Main {

	public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String one = br.readLine();
		String two = br.readLine();
		int count = 0;
		for (int i = 0; i < one.length(); i++) {
			if (one.charAt(i) != two.charAt(i)) {
				++count;
			}
		}
		System.out.println(count);

	}
} import java.io.BufferedReader; BufferedReader java.io import java.io.InputStreamReader; InputStreamReader java.io public class Main {

	public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String one = br.readLine();
		String two = br.readLine();
		int count = 0;
		for (int i = 0; i < one.length(); i++) {
			if (one.charAt(i) != two.charAt(i)) {
				++count;
			}
		}
		System.out.println(count);

	}
} Main public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String one = br.readLine();
		String two = br.readLine();
		int count = 0;
		for (int i = 0; i < one.length(); i++) {
			if (one.charAt(i) != two.charAt(i)) {
				++count;
			}
		}
		System.out.println(count);

	} main {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String one = br.readLine();
		String two = br.readLine();
		int count = 0;
		for (int i = 0; i < one.length(); i++) {
			if (one.charAt(i) != two.charAt(i)) {
				++count;
			}
		}
		System.out.println(count);

	} BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); br new BufferedReader(new InputStreamReader(System.in)) String one = br.readLine(); one br.readLine() br.readLine br String two = br.readLine(); two br.readLine() br.readLine br int count = 0; count 0 for (int i = 0; i < one.length(); i++) {
			if (one.charAt(i) != two.charAt(i)) {
				++count;
			}
		} int i = 0; int i = 0; i 0 i < one.length() i one.length() one.length one i++ i++ i {
			if (one.charAt(i) != two.charAt(i)) {
				++count;
			}
		} {
			if (one.charAt(i) != two.charAt(i)) {
				++count;
			}
		} if (one.charAt(i) != two.charAt(i)) {
				++count;
			} one.charAt(i) != two.charAt(i) one.charAt(i) one.charAt one i two.charAt(i) two.charAt two 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) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String one = br.readLine();
		String two = br.readLine();
		int count = 0;
		for (int i = 0; i < one.length(); i++) {
			if (one.charAt(i) != two.charAt(i)) {
				++count;
			}
		}
		System.out.println(count);

	}
} public class Main {

	public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String one = br.readLine();
		String two = br.readLine();
		int count = 0;
		for (int i = 0; i < one.length(); i++) {
			if (one.charAt(i) != two.charAt(i)) {
				++count;
			}
		}
		System.out.println(count);

	}
} Main


import java.io.BufferedReader;
import java.io.InputStreamReader;

public class Main {

	public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String one = br.readLine();
		String two = br.readLine();
		int count = 0;
		for (int i = 0; i < one.length(); i++) {
			if (one.charAt(i) != two.charAt(i)) {
				++count;
			}
		}
		System.out.println(count);

	}
}
