import java.io.IOException;
import java.io.InputStream;
import java.util.NoSuchElementException;

public class Main {

    public static void main(String[] args) {
        FastScanner sc = new FastScanner();

        int W = sc.nextInt();
        int H = sc.nextInt();
        int N = sc.nextInt();
        int[] S = new int[N];
        int[] K = new int[N];
        boolean[] chW = new boolean[W];
        boolean[] chH = new boolean[H];
        for (int i=0; i<N; i++) {
        	S[i] = sc.nextInt();
        	K[i] = sc.nextInt();
        	chW[S[i]-1] = true;
        	chH[K[i]-1] = true;
        }
        long cntW = 0;
        long cntH = 0;
        for (int i=0; i<W; i++) {
        	if (chW[i]) cntW++;
        }
        for (int i=0; i<H; i++) {
        	if (chH[i]) cntH++;
        }
        long ans = cntW*H + W*cntH - cntW*cntH - N;
        System.out.println(ans);

    }
}

///////////////////////////////////////////////////////

class FastScanner {
    private final InputStream in = System.in;
    private final byte[] buffer = new byte[1024];
    private int ptr = 0;
    private int buflen = 0;
    private boolean hasNextByte() {
        if (ptr < buflen) {
            return true;
        }else{
            ptr = 0;
            try {
                buflen = in.read(buffer);
            } catch (IOException e) {
                e.printStackTrace();
            }
            if (buflen <= 0) {
                return false;
            }
        }
        return true;
    }
    private int readByte() { if (hasNextByte()) return buffer[ptr++]; else return -1;}
    private boolean isPrintableChar(int c) { return 33 <= c && c <= 126;}
    private void skipUnprintable() { while(hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++;}
    public boolean hasNext() { skipUnprintable(); return hasNextByte();}
    public String next() {
        if (!hasNext()) throw new NoSuchElementException();
        StringBuilder sb = new StringBuilder();
        int b = readByte();
        while(isPrintableChar(b)) {
            sb.appendCodePoint(b);
            b = readByte();
        }
        return sb.toString();
    }
    public long nextLong() {
        if (!hasNext()) throw new NoSuchElementException();
        long n = 0;
        boolean minus = false;
        int b = readByte();
        if (b == '-') {
            minus = true;
            b = readByte();
        }
        if (b < '0' || '9' < b) {
            throw new NumberFormatException();
        }
        while(true){
            if ('0' <= b && b <= '9') {
                n *= 10;
                n += b - '0';
            }else if(b == -1 || !isPrintableChar(b)){
                return minus ? -n : n;
            }else{
                throw new NumberFormatException();
            }
            b = readByte();
        }
    }
    public int nextInt() {
        if (!hasNext()) throw new NoSuchElementException();
        int n = 0;
        boolean minus = false;
        int b = readByte();
        if (b == '-') {
            minus = true;
            b = readByte();
        }
        if (b < '0' || '9' < b) {
            throw new NumberFormatException();
        }
        while(true){
            if ('0' <= b && b <= '9') {
                n *= 10;
                n += b - '0';
            }else if(b == -1 || !isPrintableChar(b)){
                return minus ? -n : n;
            }else{
                throw new NumberFormatException();
            }
            b = readByte();
        }
    }
}