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

public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        String[] asis = reader.readLine().split("");
        String[] tobe = reader.readLine().split("");
        int i = 0;
        int count =0;
        for (String s : asis) {
            if (!s.equals(tobe[i])) {
                count++;
            }
            i++;
        }
        System.out.println(count);

    }
} 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 reader = new BufferedReader(new InputStreamReader(System.in));
        String[] asis = reader.readLine().split("");
        String[] tobe = reader.readLine().split("");
        int i = 0;
        int count =0;
        for (String s : asis) {
            if (!s.equals(tobe[i])) {
                count++;
            }
            i++;
        }
        System.out.println(count);

    }
} Main public static void main(String[] args) throws IOException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        String[] asis = reader.readLine().split("");
        String[] tobe = reader.readLine().split("");
        int i = 0;
        int count =0;
        for (String s : asis) {
            if (!s.equals(tobe[i])) {
                count++;
            }
            i++;
        }
        System.out.println(count);

    } main {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        String[] asis = reader.readLine().split("");
        String[] tobe = reader.readLine().split("");
        int i = 0;
        int count =0;
        for (String s : asis) {
            if (!s.equals(tobe[i])) {
                count++;
            }
            i++;
        }
        System.out.println(count);

    } BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); reader new BufferedReader(new InputStreamReader(System.in)) String[] asis = reader.readLine().split(""); asis reader.readLine().split("") reader.readLine().split reader.readLine() reader.readLine reader "" String[] tobe = reader.readLine().split(""); tobe reader.readLine().split("") reader.readLine().split reader.readLine() reader.readLine reader "" int i = 0; i 0 int count =0; count 0 for (String s : asis) {
            if (!s.equals(tobe[i])) {
                count++;
            }
            i++;
        } String s asis {
            if (!s.equals(tobe[i])) {
                count++;
            }
            i++;
        } {
            if (!s.equals(tobe[i])) {
                count++;
            }
            i++;
        } if (!s.equals(tobe[i])) {
                count++;
            } !s.equals(tobe[i]) s.equals(tobe[i]) s.equals s tobe[i] tobe i {
                count++;
            } count++ count i++ i 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 IOException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        String[] asis = reader.readLine().split("");
        String[] tobe = reader.readLine().split("");
        int i = 0;
        int count =0;
        for (String s : asis) {
            if (!s.equals(tobe[i])) {
                count++;
            }
            i++;
        }
        System.out.println(count);

    }
} public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        String[] asis = reader.readLine().split("");
        String[] tobe = reader.readLine().split("");
        int i = 0;
        int count =0;
        for (String s : asis) {
            if (!s.equals(tobe[i])) {
                count++;
            }
            i++;
        }
        System.out.println(count);

    }
} 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 reader = new BufferedReader(new InputStreamReader(System.in));
        String[] asis = reader.readLine().split("");
        String[] tobe = reader.readLine().split("");
        int i = 0;
        int count =0;
        for (String s : asis) {
            if (!s.equals(tobe[i])) {
                count++;
            }
            i++;
        }
        System.out.println(count);

    }
}