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

public class Main {
	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String S = br.readLine();
		String T = br.readLine();
		int l = S.length();
		int cont = 0;
		for (int i = 0; i < l; i++) {
			char s = S.charAt(i);
			char t = T.charAt(i);
			if (s != t) {
				cont++;
			}
		}
		System.out.print(cont);
	}
} import java.io.BufferedReader; BufferedReader java.io import java.io.IOException; IOException java.io import java.io.InputStreamReader; InputStreamReader java.io public class Main {
	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String S = br.readLine();
		String T = br.readLine();
		int l = S.length();
		int cont = 0;
		for (int i = 0; i < l; i++) {
			char s = S.charAt(i);
			char t = T.charAt(i);
			if (s != t) {
				cont++;
			}
		}
		System.out.print(cont);
	}
} Main public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String S = br.readLine();
		String T = br.readLine();
		int l = S.length();
		int cont = 0;
		for (int i = 0; i < l; i++) {
			char s = S.charAt(i);
			char t = T.charAt(i);
			if (s != t) {
				cont++;
			}
		}
		System.out.print(cont);
	} main {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String S = br.readLine();
		String T = br.readLine();
		int l = S.length();
		int cont = 0;
		for (int i = 0; i < l; i++) {
			char s = S.charAt(i);
			char t = T.charAt(i);
			if (s != t) {
				cont++;
			}
		}
		System.out.print(cont);
	} BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); br new BufferedReader(new InputStreamReader(System.in)) String S = br.readLine(); S br.readLine() br.readLine br String T = br.readLine(); T br.readLine() br.readLine br int l = S.length(); l S.length() S.length S int cont = 0; cont 0 for (int i = 0; i < l; i++) {
			char s = S.charAt(i);
			char t = T.charAt(i);
			if (s != t) {
				cont++;
			}
		} int i = 0; int i = 0; i 0 i < l i l i++ i++ i {
			char s = S.charAt(i);
			char t = T.charAt(i);
			if (s != t) {
				cont++;
			}
		} {
			char s = S.charAt(i);
			char t = T.charAt(i);
			if (s != t) {
				cont++;
			}
		} char s = S.charAt(i); s S.charAt(i) S.charAt S i char t = T.charAt(i); t T.charAt(i) T.charAt T i if (s != t) {
				cont++;
			} s != t s t {
				cont++;
			} cont++ cont System.out.print(cont) System.out.print System.out System System.out cont String[] args args public class Main {
	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String S = br.readLine();
		String T = br.readLine();
		int l = S.length();
		int cont = 0;
		for (int i = 0; i < l; i++) {
			char s = S.charAt(i);
			char t = T.charAt(i);
			if (s != t) {
				cont++;
			}
		}
		System.out.print(cont);
	}
} public class Main {
	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String S = br.readLine();
		String T = br.readLine();
		int l = S.length();
		int cont = 0;
		for (int i = 0; i < l; i++) {
			char s = S.charAt(i);
			char t = T.charAt(i);
			if (s != t) {
				cont++;
			}
		}
		System.out.print(cont);
	}
} Main
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {
	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String S = br.readLine();
		String T = br.readLine();
		int l = S.length();
		int cont = 0;
		for (int i = 0; i < l; i++) {
			char s = S.charAt(i);
			char t = T.charAt(i);
			if (s != t) {
				cont++;
			}
		}
		System.out.print(cont);
	}
}