import java.io.*;
// import java.math.*;
import java.util.*;
// import java.util.Map.*;
// import java.util.stream.*;

@SuppressWarnings ("unchecked")
public class Main {
    public static <T> List<List<T>> zip (List<T>... lists) {
        List<List<T>> zipped = new ArrayList<List<T>>();
        for (List<T> list : lists) {
            for (int i = 0, listSize = list.size(); i < listSize; i++) {
                List<T> list2;
                if (i >= zipped.size())
                    zipped.add (list2 = new ArrayList<T>());
                else
                    list2 = zipped.get (i);
                list2.add (list.get (i));
            }
        }
        return zipped;
    }
    static List<Character> toCharacterList (String s) {
        if (s == null) {
            return null;
        }
        int len = s.length();
        List<Character> lst = new ArrayList<Character>();
        for (int i = 0; i < len; i++) {
            lst.add (Character.valueOf (s.charAt (i)));
        }
        return lst;
    }
    public static void main (String[] args) throws Exception {
        BufferedReader reader =
            new BufferedReader (new InputStreamReader (System.in));
        List<Character> S = toCharacterList (reader.readLine());
        List<Character> T = toCharacterList (reader.readLine());
        List<List<Character>> z = zip (S, T);
        int ans = 0;
        for (List<Character> v : z) {
            if (!v.get (0).equals (v.get (1)))
                ans++;
        }
        System.out.println (ans);
        return;
    }
} import java.io.*; io.* java import java.util.*; util.* java public class Main {
    public static <T> List<List<T>> zip (List<T>... lists) {
        List<List<T>> zipped = new ArrayList<List<T>>();
        for (List<T> list : lists) {
            for (int i = 0, listSize = list.size(); i < listSize; i++) {
                List<T> list2;
                if (i >= zipped.size())
                    zipped.add (list2 = new ArrayList<T>());
                else
                    list2 = zipped.get (i);
                list2.add (list.get (i));
            }
        }
        return zipped;
    }
    static List<Character> toCharacterList (String s) {
        if (s == null) {
            return null;
        }
        int len = s.length();
        List<Character> lst = new ArrayList<Character>();
        for (int i = 0; i < len; i++) {
            lst.add (Character.valueOf (s.charAt (i)));
        }
        return lst;
    }
    public static void main (String[] args) throws Exception {
        BufferedReader reader =
            new BufferedReader (new InputStreamReader (System.in));
        List<Character> S = toCharacterList (reader.readLine());
        List<Character> T = toCharacterList (reader.readLine());
        List<List<Character>> z = zip (S, T);
        int ans = 0;
        for (List<Character> v : z) {
            if (!v.get (0).equals (v.get (1)))
                ans++;
        }
        System.out.println (ans);
        return;
    }
} Main public static <T> List<List<T>> zip (List<T>... lists) {
        List<List<T>> zipped = new ArrayList<List<T>>();
        for (List<T> list : lists) {
            for (int i = 0, listSize = list.size(); i < listSize; i++) {
                List<T> list2;
                if (i >= zipped.size())
                    zipped.add (list2 = new ArrayList<T>());
                else
                    list2 = zipped.get (i);
                list2.add (list.get (i));
            }
        }
        return zipped;
    } zip {
        List<List<T>> zipped = new ArrayList<List<T>>();
        for (List<T> list : lists) {
            for (int i = 0, listSize = list.size(); i < listSize; i++) {
                List<T> list2;
                if (i >= zipped.size())
                    zipped.add (list2 = new ArrayList<T>());
                else
                    list2 = zipped.get (i);
                list2.add (list.get (i));
            }
        }
        return zipped;
    } List<List<T>> zipped = new ArrayList<List<T>>(); zipped new ArrayList<List<T>>() for (List<T> list : lists) {
            for (int i = 0, listSize = list.size(); i < listSize; i++) {
                List<T> list2;
                if (i >= zipped.size())
                    zipped.add (list2 = new ArrayList<T>());
                else
                    list2 = zipped.get (i);
                list2.add (list.get (i));
            }
        } List<T> list lists {
            for (int i = 0, listSize = list.size(); i < listSize; i++) {
                List<T> list2;
                if (i >= zipped.size())
                    zipped.add (list2 = new ArrayList<T>());
                else
                    list2 = zipped.get (i);
                list2.add (list.get (i));
            }
        } {
            for (int i = 0, listSize = list.size(); i < listSize; i++) {
                List<T> list2;
                if (i >= zipped.size())
                    zipped.add (list2 = new ArrayList<T>());
                else
                    list2 = zipped.get (i);
                list2.add (list.get (i));
            }
        } for (int i = 0, listSize = list.size(); i < listSize; i++) {
                List<T> list2;
                if (i >= zipped.size())
                    zipped.add (list2 = new ArrayList<T>());
                else
                    list2 = zipped.get (i);
                list2.add (list.get (i));
            } int i = 0, listSize = list.size(); int i = 0 i 0 listSize = list.size(); listSize list.size() list.size list i < listSize i listSize i++ i++ i {
                List<T> list2;
                if (i >= zipped.size())
                    zipped.add (list2 = new ArrayList<T>());
                else
                    list2 = zipped.get (i);
                list2.add (list.get (i));
            } {
                List<T> list2;
                if (i >= zipped.size())
                    zipped.add (list2 = new ArrayList<T>());
                else
                    list2 = zipped.get (i);
                list2.add (list.get (i));
            } List<T> list2; list2 if (i >= zipped.size())
                    zipped.add (list2 = new ArrayList<T>());
                else
                    list2 = zipped.get (i); i >= zipped.size() i zipped.size() zipped.size zipped zipped.add (list2 = new ArrayList<T>()) zipped.add zipped list2 = new ArrayList<T>() list2 new ArrayList<T>() list2 = zipped.get (i) list2 zipped.get (i) zipped.get zipped i list2.add (list.get (i)) list2.add list2 list.get (i) list.get list i return zipped; zipped List<T>... lists lists static List<Character> toCharacterList (String s) {
        if (s == null) {
            return null;
        }
        int len = s.length();
        List<Character> lst = new ArrayList<Character>();
        for (int i = 0; i < len; i++) {
            lst.add (Character.valueOf (s.charAt (i)));
        }
        return lst;
    } toCharacterList {
        if (s == null) {
            return null;
        }
        int len = s.length();
        List<Character> lst = new ArrayList<Character>();
        for (int i = 0; i < len; i++) {
            lst.add (Character.valueOf (s.charAt (i)));
        }
        return lst;
    } if (s == null) {
            return null;
        } s == null s null {
            return null;
        } return null; null int len = s.length(); len s.length() s.length s List<Character> lst = new ArrayList<Character>(); lst new ArrayList<Character>() for (int i = 0; i < len; i++) {
            lst.add (Character.valueOf (s.charAt (i)));
        } int i = 0; int i = 0; i 0 i < len i len i++ i++ i {
            lst.add (Character.valueOf (s.charAt (i)));
        } {
            lst.add (Character.valueOf (s.charAt (i)));
        } lst.add (Character.valueOf (s.charAt (i))) lst.add lst Character.valueOf (s.charAt (i)) Character.valueOf Character s.charAt (i) s.charAt s i return lst; lst String s s public static void main (String[] args) throws Exception {
        BufferedReader reader =
            new BufferedReader (new InputStreamReader (System.in));
        List<Character> S = toCharacterList (reader.readLine());
        List<Character> T = toCharacterList (reader.readLine());
        List<List<Character>> z = zip (S, T);
        int ans = 0;
        for (List<Character> v : z) {
            if (!v.get (0).equals (v.get (1)))
                ans++;
        }
        System.out.println (ans);
        return;
    } main {
        BufferedReader reader =
            new BufferedReader (new InputStreamReader (System.in));
        List<Character> S = toCharacterList (reader.readLine());
        List<Character> T = toCharacterList (reader.readLine());
        List<List<Character>> z = zip (S, T);
        int ans = 0;
        for (List<Character> v : z) {
            if (!v.get (0).equals (v.get (1)))
                ans++;
        }
        System.out.println (ans);
        return;
    } BufferedReader reader =
            new BufferedReader (new InputStreamReader (System.in)); reader new BufferedReader (new InputStreamReader (System.in)) List<Character> S = toCharacterList (reader.readLine()); S toCharacterList (reader.readLine()) toCharacterList reader.readLine() reader.readLine reader List<Character> T = toCharacterList (reader.readLine()); T toCharacterList (reader.readLine()) toCharacterList reader.readLine() reader.readLine reader List<List<Character>> z = zip (S, T); z zip (S, T) zip S T int ans = 0; ans 0 for (List<Character> v : z) {
            if (!v.get (0).equals (v.get (1)))
                ans++;
        } List<Character> v z {
            if (!v.get (0).equals (v.get (1)))
                ans++;
        } {
            if (!v.get (0).equals (v.get (1)))
                ans++;
        } if (!v.get (0).equals (v.get (1)))
                ans++; !v.get (0).equals (v.get (1)) v.get (0).equals (v.get (1)) v.get (0).equals v.get (0) v.get v 0 v.get (1) v.get v 1 ans++ ans System.out.println (ans) System.out.println System.out System System.out ans return; String[] args args public class Main {
    public static <T> List<List<T>> zip (List<T>... lists) {
        List<List<T>> zipped = new ArrayList<List<T>>();
        for (List<T> list : lists) {
            for (int i = 0, listSize = list.size(); i < listSize; i++) {
                List<T> list2;
                if (i >= zipped.size())
                    zipped.add (list2 = new ArrayList<T>());
                else
                    list2 = zipped.get (i);
                list2.add (list.get (i));
            }
        }
        return zipped;
    }
    static List<Character> toCharacterList (String s) {
        if (s == null) {
            return null;
        }
        int len = s.length();
        List<Character> lst = new ArrayList<Character>();
        for (int i = 0; i < len; i++) {
            lst.add (Character.valueOf (s.charAt (i)));
        }
        return lst;
    }
    public static void main (String[] args) throws Exception {
        BufferedReader reader =
            new BufferedReader (new InputStreamReader (System.in));
        List<Character> S = toCharacterList (reader.readLine());
        List<Character> T = toCharacterList (reader.readLine());
        List<List<Character>> z = zip (S, T);
        int ans = 0;
        for (List<Character> v : z) {
            if (!v.get (0).equals (v.get (1)))
                ans++;
        }
        System.out.println (ans);
        return;
    }
} public class Main {
    public static <T> List<List<T>> zip (List<T>... lists) {
        List<List<T>> zipped = new ArrayList<List<T>>();
        for (List<T> list : lists) {
            for (int i = 0, listSize = list.size(); i < listSize; i++) {
                List<T> list2;
                if (i >= zipped.size())
                    zipped.add (list2 = new ArrayList<T>());
                else
                    list2 = zipped.get (i);
                list2.add (list.get (i));
            }
        }
        return zipped;
    }
    static List<Character> toCharacterList (String s) {
        if (s == null) {
            return null;
        }
        int len = s.length();
        List<Character> lst = new ArrayList<Character>();
        for (int i = 0; i < len; i++) {
            lst.add (Character.valueOf (s.charAt (i)));
        }
        return lst;
    }
    public static void main (String[] args) throws Exception {
        BufferedReader reader =
            new BufferedReader (new InputStreamReader (System.in));
        List<Character> S = toCharacterList (reader.readLine());
        List<Character> T = toCharacterList (reader.readLine());
        List<List<Character>> z = zip (S, T);
        int ans = 0;
        for (List<Character> v : z) {
            if (!v.get (0).equals (v.get (1)))
                ans++;
        }
        System.out.println (ans);
        return;
    }
} Main
import java.io.*;
// import java.math.*;
import java.util.*;
// import java.util.Map.*;
// import java.util.stream.*;

@SuppressWarnings ("unchecked")
public class Main {
    public static <T> List<List<T>> zip (List<T>... lists) {
        List<List<T>> zipped = new ArrayList<List<T>>();
        for (List<T> list : lists) {
            for (int i = 0, listSize = list.size(); i < listSize; i++) {
                List<T> list2;
                if (i >= zipped.size())
                    zipped.add (list2 = new ArrayList<T>());
                else
                    list2 = zipped.get (i);
                list2.add (list.get (i));
            }
        }
        return zipped;
    }
    static List<Character> toCharacterList (String s) {
        if (s == null) {
            return null;
        }
        int len = s.length();
        List<Character> lst = new ArrayList<Character>();
        for (int i = 0; i < len; i++) {
            lst.add (Character.valueOf (s.charAt (i)));
        }
        return lst;
    }
    public static void main (String[] args) throws Exception {
        BufferedReader reader =
            new BufferedReader (new InputStreamReader (System.in));
        List<Character> S = toCharacterList (reader.readLine());
        List<Character> T = toCharacterList (reader.readLine());
        List<List<Character>> z = zip (S, T);
        int ans = 0;
        for (List<Character> v : z) {
            if (!v.get (0).equals (v.get (1)))
                ans++;
        }
        System.out.println (ans);
        return;
    }
}