// template {{{

#include <bits/stdc++.h>
using namespace std;

// #define int long long

#define GET_MACRO(a, b, c, d, NAME, ...) NAME
#define REP2(i, n) REP3(i, 0, n)
#define REP3(i, a, b) REP4(i, a, b, 1)
#define REP4(i, a, b, s) for (int i = (a); i < (int)(b); i += s)
#define RREP2(i, n) RREP3(i, 0, n)
#define RREP3(i, a, b) for (int i = (b) - 1; i >= (int)(a); i--)

#define rep(...) GET_MACRO(__VA_ARGS__, REP4, REP3, REP2)(__VA_ARGS__)
#define rrep(...) GET_MACRO(__VA_ARGS__,, RREP3, RREP2)(__VA_ARGS__)
#define eb emplace_back
#define ef emplace_front
#define pb pop_back
#define pf pop_front
#define all(c) std::begin(c), std::end(c)
#define fi first
#define se second
#define popcnt __builtin_popcountll

using uint = unsigned;
using ll = long long;
using ull = unsigned long long;
using ld = long double;
using vi = std::vector<int>;
using vvi = std::vector<vi>;

template<typename T>
using maxpq = std::priority_queue<T, std::vector<T>, std::less<T>>;

template<typename T>
using minpq = std::priority_queue<T, std::vector<T>, std::greater<T>>;

const int INF = 1e9 + 10;
const ll LLINF = 1e18 + 10;

const int dx[] = {-1, 0, 1, 0};
const int dy[] = {0, -1, 0, 1};
const int dx8[] = {-1, -1, 0, 1, 1, 1, 0, -1};
const int dy8[] = {0, -1, -1, -1, 0, 1, 1, 1};

template<typename T>
inline T sq(T x){ return x * x; }

template<typename T, typename U>
inline bool chmax(T &x, U y){ if (x >= y) return false; x = y; return true; }

template<typename T, typename U>
inline bool chmin(T &x, U y){ if (x <= y) return false; x = y; return true; }

template<typename T>
inline T& sort(T &c){ sort(all(c)); return c; }

template<typename T>
inline T& reverse(T &c){ reverse(all(c)); return c; }

template<typename T>
inline T& rsort(T &c){ sort(all(c), greater<T>()); return c; }

template<typename T>
inline T& unique(T &c){ sort(all(c)); c.erase(unique(all(c)), end(c)); return c; }

// }}}

ll w, h, n;
set<ll> x, y;

int main()
{
	cin >> w >> h >> n;
	rep(i, n){
		int s, k;
		cin >> s >> k;
		x.emplace(s);
		y.emplace(k);
	}
	cout << x.size() * h + y.size() * w - (ll)x.size() * y.size() - n << endl;
}