import java.io.*;
import java.util.*;
import java.util.stream.IntStream;


public class Main {


    public static class BonusSolver {
        private final List<Book> books;
        private final List<Object> maxMatch;
        private final HashMap<Book, Category> assignedCategory;
        private final HashMap<Category, Book> assignedBook;
        private final HashMap<Book, Boolean> visited;

        public BonusSolver(List<Book> books) {
            this.books = books;
            this.visited = new HashMap<>();
            this.assignedBook = new HashMap<>();
            this.assignedCategory = new HashMap<>();
            this.maxMatch = new LinkedList<>();
        }

        private boolean getMatch(Book book) {
            if (visited.get(book)) {
                return false;
            }
            visited.put(book, true);
            for (int i = 0; i < book.getNumberOfCategories(); ++i) {
                if (!assignedBook.containsKey(book.getCategory(i))) {
                    assignedCategory.put(book, book.getCategory(i));
                    assignedBook.put(book.getCategory(i), book);
                    return true;
                }
            }
            for (int i = 0; i < book.getNumberOfCategories(); ++i) {
                if (getMatch(assignedBook.get(book.getCategory(i)))) {
                    assignedCategory.put(book, book.getCategory(i));
                    assignedBook.put(book.getCategory(i), book);
                    return true;
                }
            }
            return false;
        }

        public void runHopcroftKarp() {
            boolean change = true;
            while (change) {
                change = false;
                for (Book book : books) {
                    visited.put(book, false);
                }
                for (Book book : books) {
                    if (!assignedCategory.containsKey(book)) {
                        change |= getMatch(book);
                    }
                }
                visited.clear();
            }
            for (Book book : books) {
                if (assignedCategory.containsKey(book)) {
                    maxMatch.add(book);
                    maxMatch.add(assignedCategory.get(book));
                }
            }
        }

        public List<Object> getMaxMatching() {
            return maxMatch;
        }

    }


    public static class Book {
        private final Integer index;
        private final List<Category> categories;

        public Book(int index, String name) {
            this.index = index;
            this.categories = new LinkedList<>();
        }

        public Integer getIndex() {
            return index;
        }

        public void addCategory(Category category) {
            categories.add(category);
        }

        public int getNumberOfCategories() {
            return categories.size();
        }

        public Category getCategory(int index) {
            return categories.get(index);
        }

    }

    public static class Category {
        private final Integer index;

        public Category(int index, String name) {
            this.index = index;
        }

        public Integer getIndex() {
            return index;
        }
    }


    public static class Library {
        private final List<Book> books;
        private final List<Category> categories;

        Library() {
            books = new LinkedList<>();
            categories = new ArrayList<>();
        }

        public void addBook(Book book) {
            books.add(book);
        }

        public void addCategory(Category category) {
            categories.add(category);
        }

        public Book getBook(int index) {
            return books.get(index);
        }

        public Category getCategory(int index) {
            return categories.get(index);
        }

        public void addLink(Book book, Category category) {
            book.addCategory(category);
        }

        public List<Book> getBooks() {
            return books;
        }

    }

    public static class InputReader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;

        public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream), 32768);
            tokenizer = null;
        }

        public String next() {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }

        public int nextInt() {
            return Integer.parseInt(next());
        }
    }

    public static void main(String[] args) throws FileNotFoundException {
        InputReader in = new InputReader(new FileInputStream("fmcm.in"));
        PrintWriter out = new PrintWriter(new FileOutputStream("fmcm.out"));
        Library library = new Library();
        IntStream.rangeClosed(1, in.nextInt())
                .mapToObj(i -> new Book(i, "B" + i))
                .forEach(library::addBook);
        IntStream.rangeClosed(1, in.nextInt())
                .mapToObj(i -> new Category(i, "C" + i))
                .forEach(library::addCategory);
        int edges = in.nextInt();
        for (; edges > 0; --edges) {
            library.addLink(library.getBook(in.nextInt() - 1), library.getCategory(in.nextInt() - 1));
        }
        BonusSolver bonusSolver = new BonusSolver(library.getBooks());
        bonusSolver.runHopcroftKarp();
        List<Object> maxMatch = bonusSolver.getMaxMatching();
        out.println(maxMatch.size() >> 1);
        for (int i = 0; i < maxMatch.size(); i += 2) {
            out.println(((Book) maxMatch.get(i)).getIndex() + " " + ((Category) maxMatch.get(i + 1)).getIndex());
        }
        out.close();
    }
}