//#include <bits/stdc++.h>
#include <assert.h>
#include <algorithm>
#include <cmath>
#include <cstring>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
#include <iterator>
#include <unistd.h>

using namespace std;

typedef signed long long ll;

#define pp(...) (void)printf(__VA_ARGS__)
#define For(x,to) for(x=0;x<(to);x++)
#define ForAuto(x,arr) for(auto& x:arr)
#define ForBeginEnd(x,c) for(__typeof(c.begin()) x=c.begin();x!=c.end();x++)
#define All(a) (a.begin()),(a.end())
#define Zeros(a) memset(a,0,sizeof(a))
#define Minus(a) memset(a,0xff,sizeof(a))

#define PI 3.14159265
#define EPS (1e-10)
#define EPS_eq(a,b) (abs((a)-(b)) < EPS)

#pragma GCC diagnostic ignored "-Wconversion"

//#define int long long
#define INF 1000*1000

int dxy[] = {0, 1, 0, -1, 0};

typedef pair<int, int> P;

void pp_int(int x){ printf("%d\n", x); };

int i,j,k;

ll M = 100000009;

//ios::sync_with_stdio(false);

//-------------------------------------------------

set <ll> sets, setk;

signed main() {
    ll W,H,N;
    cin>>W>>H>>N;

    for(int i=0;i<N;i++){
        ll S,K;
        cin>>S>>K;
        sets.insert(S);
        setk.insert(K);
    }

    ll res = -N;
    res += H * sets.size();
    res += W * setk.size();
    res -= sets.size();

    cout<<res<<endl;

    return 0;
}