import java.util.Scanner;
import java.util.Arrays;

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

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