#include<bits/stdc++.h>
typedef long long ll;
typedef unsigned long long ull;
using namespace std;
#define pb push_back
int dy[]={0, 0, 1, -1, 1, 1, -1, -1};
int dx[]={1, -1, 0, 0, 1, -1, -1, 1};

#define FOR(i,a,b) for (int i=(a);i<(b);i++)
#define RFOR(i,a,b) for (int i=(b)-1;i>=(a);i--)
#define REP(i,n) for (int i=0;i<(n);i++)
#define RREP(i,n) for (int i=(n)-1;i>=0;i--)
#define mp make_pair
#define fi first
#define sc second
ll w,h,n;
ll s[200],k[200];


int main(void){
	cin >> w >> h >> n;
	REP(i,n){
		cin >> s[i] >> k[i];
	}

	vector<ll > sv;
	REP(i,n){
		bool f = true;
		REP(j,sv.size())
			if(s[i] == sv[j]){
				f = false;
				break;
			}
		if(f)
			sv.pb(s[i]);
	}
	vector<ll > kv;
	REP(i,n){
		bool f = true;
		REP(j,kv.size())
			if(k[i] == kv[j]){
				f = false;
				break;
			}
		if(f)
			kv.pb(k[i]);
	}

	cout << w * h - (w - sv.size()) * (h - kv.size()) - n << endl;
	return 0;
}