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

using Int8 = int8_t; using Int16 = int16_t; using Int32 = int32_t; using Int64 = int64_t; using Int128 = __int128_t;
using Word8 = uint8_t; using Word16 = uint16_t; using Word32 = uint32_t; using Word64 = uint64_t; using Word128 = __uint128_t;
using Int = int_fast64_t;
using Word = uint_fast64_t;
using VI = vector<Int>; using VW = vector<Word>; using VVI = vector<VI>; using VVW = vector<VW>;
using F32 = float; using F64 = double; using F80 = long double;
using PII = pair<Int,Int>; using PWW = pair<Word,Word>; using VPII = vector<PII>; using VPWW = vector<PWW>;
using VS = vector<string>; using VVS = vector<VS>; using VB = vector<bool>; using VVB = vector<VB>;

#define rep(i,n) for(Int i=0,i##_len=(n); i<i##_len ; i++)
#define reps(i,n) for(Int i=0,i##_len=(n); i<=i##_len; i++)
#define Range(i,a,b) for(Int i=(a); i<=(b); i++)
#define SZ(obj) ((Int)obj.size())
#define ALL(obj) (obj).begin(),(obj).end()
#define RALL(obj) (obj).rbegin(),(obj).rend()
#define UNIQUE(obj) (obj).erase(unique((obj).begin(), (obj).end()), (obj).end())

int main() {
  Int W, H, N;
  cin >> W >> H >> N;
  set<Int> sw, sh;
  rep(i,N) {
    Int S, K;
    cin >> S >> K;
    sw.insert(S);
    sh.insert(K);
  }
  Int w = SZ(sw), h = SZ(sh);
  cout << (w * H + h * W - w * h - N) << endl;
  return 0;
}