import java.util.Scanner;

public class Main {
  public static void main(String[] args) {
    int ans = 0;
    Scanner sc = new Scanner(System.in);
    char[] s = sc.next().toCharArray();
    char[] t = sc.next().toCharArray();
    for (int cnt = 0; cnt < s.length; cnt++) {
      if (s[cnt] != t[cnt]) {
        ans++;
      }
    }
    System.out.println(ans + "");
    sc.close();
  }
} import java.util.Scanner; Scanner java.util public class Main {
  public static void main(String[] args) {
    int ans = 0;
    Scanner sc = new Scanner(System.in);
    char[] s = sc.next().toCharArray();
    char[] t = sc.next().toCharArray();
    for (int cnt = 0; cnt < s.length; cnt++) {
      if (s[cnt] != t[cnt]) {
        ans++;
      }
    }
    System.out.println(ans + "");
    sc.close();
  }
} Main public static void main(String[] args) {
    int ans = 0;
    Scanner sc = new Scanner(System.in);
    char[] s = sc.next().toCharArray();
    char[] t = sc.next().toCharArray();
    for (int cnt = 0; cnt < s.length; cnt++) {
      if (s[cnt] != t[cnt]) {
        ans++;
      }
    }
    System.out.println(ans + "");
    sc.close();
  } main {
    int ans = 0;
    Scanner sc = new Scanner(System.in);
    char[] s = sc.next().toCharArray();
    char[] t = sc.next().toCharArray();
    for (int cnt = 0; cnt < s.length; cnt++) {
      if (s[cnt] != t[cnt]) {
        ans++;
      }
    }
    System.out.println(ans + "");
    sc.close();
  } int ans = 0; ans 0 Scanner sc = new Scanner(System.in); sc new Scanner(System.in) char[] s = sc.next().toCharArray(); s sc.next().toCharArray() sc.next().toCharArray sc.next() sc.next sc char[] t = sc.next().toCharArray(); t sc.next().toCharArray() sc.next().toCharArray sc.next() sc.next sc for (int cnt = 0; cnt < s.length; cnt++) {
      if (s[cnt] != t[cnt]) {
        ans++;
      }
    } int cnt = 0; int cnt = 0; cnt 0 cnt < s.length cnt s.length s s.length cnt++ cnt++ cnt {
      if (s[cnt] != t[cnt]) {
        ans++;
      }
    } {
      if (s[cnt] != t[cnt]) {
        ans++;
      }
    } if (s[cnt] != t[cnt]) {
        ans++;
      } s[cnt] != t[cnt] s[cnt] s cnt t[cnt] t cnt {
        ans++;
      } ans++ ans System.out.println(ans + "") System.out.println System.out System System.out ans + "" ans "" sc.close() sc.close sc String[] args args public class Main {
  public static void main(String[] args) {
    int ans = 0;
    Scanner sc = new Scanner(System.in);
    char[] s = sc.next().toCharArray();
    char[] t = sc.next().toCharArray();
    for (int cnt = 0; cnt < s.length; cnt++) {
      if (s[cnt] != t[cnt]) {
        ans++;
      }
    }
    System.out.println(ans + "");
    sc.close();
  }
} public class Main {
  public static void main(String[] args) {
    int ans = 0;
    Scanner sc = new Scanner(System.in);
    char[] s = sc.next().toCharArray();
    char[] t = sc.next().toCharArray();
    for (int cnt = 0; cnt < s.length; cnt++) {
      if (s[cnt] != t[cnt]) {
        ans++;
      }
    }
    System.out.println(ans + "");
    sc.close();
  }
} Main
import java.util.Scanner;

public class Main {
  public static void main(String[] args) {
    int ans = 0;
    Scanner sc = new Scanner(System.in);
    char[] s = sc.next().toCharArray();
    char[] t = sc.next().toCharArray();
    for (int cnt = 0; cnt < s.length; cnt++) {
      if (s[cnt] != t[cnt]) {
        ans++;
      }
    }
    System.out.println(ans + "");
    sc.close();
  }
}
