import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String str = sc.nextLine();
        String[] S = str.split("");
        String str2 = sc.nextLine();
        String[] T = str2.split("");
        int c = 0;
        for (int i = 0; i < S.length; i++) {
            if ( S[i].equals(T[i]) ) {
                c = c;
            } else {
                c = c+1;
            }
        }
        System.out.println(c);
    }
} import java.util.Scanner; Scanner java.util public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String str = sc.nextLine();
        String[] S = str.split("");
        String str2 = sc.nextLine();
        String[] T = str2.split("");
        int c = 0;
        for (int i = 0; i < S.length; i++) {
            if ( S[i].equals(T[i]) ) {
                c = c;
            } else {
                c = c+1;
            }
        }
        System.out.println(c);
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String str = sc.nextLine();
        String[] S = str.split("");
        String str2 = sc.nextLine();
        String[] T = str2.split("");
        int c = 0;
        for (int i = 0; i < S.length; i++) {
            if ( S[i].equals(T[i]) ) {
                c = c;
            } else {
                c = c+1;
            }
        }
        System.out.println(c);
    } main {
        Scanner sc = new Scanner(System.in);
        String str = sc.nextLine();
        String[] S = str.split("");
        String str2 = sc.nextLine();
        String[] T = str2.split("");
        int c = 0;
        for (int i = 0; i < S.length; i++) {
            if ( S[i].equals(T[i]) ) {
                c = c;
            } else {
                c = c+1;
            }
        }
        System.out.println(c);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String str = sc.nextLine(); str sc.nextLine() sc.nextLine sc String[] S = str.split(""); S str.split("") str.split str "" String str2 = sc.nextLine(); str2 sc.nextLine() sc.nextLine sc String[] T = str2.split(""); T str2.split("") str2.split str2 "" int c = 0; c 0 for (int i = 0; i < S.length; i++) {
            if ( S[i].equals(T[i]) ) {
                c = c;
            } else {
                c = c+1;
            }
        } int i = 0; int i = 0; i 0 i < S.length i S.length S S.length i++ i++ i {
            if ( S[i].equals(T[i]) ) {
                c = c;
            } else {
                c = c+1;
            }
        } {
            if ( S[i].equals(T[i]) ) {
                c = c;
            } else {
                c = c+1;
            }
        } if ( S[i].equals(T[i]) ) {
                c = c;
            } else {
                c = c+1;
            } S[i].equals(T[i]) S[i].equals S[i] S i T[i] T i {
                c = c;
            } c = c c c {
                c = c+1;
            } c = c+1 c c+1 c 1 System.out.println(c) System.out.println System.out System System.out c String[] args args public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String str = sc.nextLine();
        String[] S = str.split("");
        String str2 = sc.nextLine();
        String[] T = str2.split("");
        int c = 0;
        for (int i = 0; i < S.length; i++) {
            if ( S[i].equals(T[i]) ) {
                c = c;
            } else {
                c = c+1;
            }
        }
        System.out.println(c);
    }
} public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String str = sc.nextLine();
        String[] S = str.split("");
        String str2 = sc.nextLine();
        String[] T = str2.split("");
        int c = 0;
        for (int i = 0; i < S.length; i++) {
            if ( S[i].equals(T[i]) ) {
                c = c;
            } else {
                c = c+1;
            }
        }
        System.out.println(c);
    }
} Main
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String str = sc.nextLine();
        String[] S = str.split("");
        String str2 = sc.nextLine();
        String[] T = str2.split("");
        int c = 0;
        for (int i = 0; i < S.length; i++) {
            if ( S[i].equals(T[i]) ) {
                c = c;
            } else {
                c = c+1;
            }
        }
        System.out.println(c);
    }
}