#include <bits/stdc++.h>
using namespace std;
#pragma GCC target("avx2")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
template<typename T> inline bool chmax(T &a, T b) { return ((a < b) ? (a = b, true) : (false)); }
template<typename T> inline bool chmin(T &a, T b) { return ((a > b) ? (a = b, true) : (false)); }
#define rep(i, n) for (int i = 0; i < (long long)(n); i++)
#define rep2(i, m ,n) for (int i = (m); i < (long long)(n); i++)
#define REP(i, n) for (long long i = 1; i < (long long)(n); i++)
typedef long long ll;
#define updiv(N,X) (N + X - 1) / X
#define l(n) n.begin(),n.end()
#define YesNo(Q) Q==1?cout<<"Yes":cout<<"No"
using P = pair<int, int>;
const int MOD = 998244353LL;

template <int D> struct fast_set {
	static_assert(1 <= D && D <= 6);
	using U = uint64_t;

	int n;
	std::array<std::vector<U>, D> a;
	fast_set(int n_ = 0) : n(n_) {
		assert(0 <= n && n <= int64_t(1) << (6*D));
		int m = n ? n : 1;
		for (int d = 0; d < D; d++) {
			m = (m + 63) >> 6;
			a[d].assign(m, 0);
		}
	}

	bool empty() const {
		return !a[D-1][0];
	}

	bool contains(int i) const {
		return (a[0][i >> 6] >> (i & 63)) & 1;
	}

	void insert(int i) {
		for (int d = 0; d < D; d++) {
			int q = i >> 6, r = i & 63;
			a[d][q] |= U(1) << r;
			i = q;
		}
	}

	void erase(int i) {
		for (int d = 0; d < D; d++) {
			int q = i >> 6, r = i & 63;
			if ((a[d][q] &= ~(U(1) << r))) break;
			i = q;
		}
	}

	int next(int i) const {
		for (int d = 0; d < D; d++) {
			int q = i >> 6, r = i & 63;
			if (q >= int(a[d].size())) break;
			U upper = a[d][q] >> r;
			if (upper) {
				i += __builtin_ctzll(upper);
				for (int e = d-1; e >= 0; e--) {
					i = i << 6 | __builtin_ctzll(a[e][i]);
				}
				return i;
			}
			i = q+1;
		}
		return n;
	}

	int prev(int i) const {
		for (int d = 0; d < D; d++) {
			if (i < 0) break;
			int q = i >> 6, r = i & 63;
			U lower = a[d][q] << (63-r);
			if (lower) {
				i -= __builtin_clzll(lower);
				for (int e = d-1; e >= 0; e--) {
					i = i << 6 | (63 - __builtin_clzll(a[e][i]));
				}
				return i;
			}
			i = q-1;
		}
		return -1;
	}
};

ll solve(vector<int> &w){
fast_set<2> st(w.size());
vector<pair<ll,ll>> v(w.size());
rep(i,w.size()){v[i] = pair(w[i],i);}
sort(l(v));
int n = w.size();
ll ans = 0;
rep(i,n){
  auto t = st.next(v[i].second);
  auto k = st.prev(v[i].second);
  ans += (v[i].second-(ll)(k)) * ((ll)(t)-v[i].second) * v[i].first;
  st.insert(v[i].second);
}
return ans;
}

int main(){
  ll h,w,n;cin>>h>>w>>n;
  vector<vector<int>> v(h,vector<int>(w,0));
  rep(i,n){
  int a,b;cin>>a>>b;a--;b--;
  v[a][b] = 1;
  }
//  otp(v);
  //vector<vector<ll>> t(h,vector<ll>(w,0));
  rep(i,w){
    ll now = 0;
    rep(j,h){now++;if(v[h-j-1][i]==1){now = 0;}v[h-j-1][i] = now;}
  }
 // otp(v);
  ll ans = 0;
  rep(i,h){
   // rep(j,h){cout << w[j] << " ";}cout<<endl;
    ans += solve(v[i]);
   // cout << solve(w).val() << endl;
  }
 // vector<ll> y={2,1,3,4,5};
  //cout << solve(y) << endl;
  //cout << solveg(y) << endl;
  cout << ans << endl;
}