#include <cstdio>
#include <cstdlib>
#include <iostream>
#include <string>
#include <cmath>
#include <algorithm>
#include <vector>
#include <queue>
#include <stack>
#include <map>
#include <set>
#include <cstring>

typedef long long ll;
using namespace std;

#define mod 1000000007
#define INF 1000000000
#define LLINF 2000000000000000000LL

#define SIZE 1000000

int cards_s[SIZE],cards_k[SIZE];
int in_s[100],in_k[100];

int main(){
    int n,w,h,H,W;
    
    scanf("%d%d%d",&w,&h,&n);
    
    H=h;
    W=w;
    
    for(int i=0;i<n;i++){
        scanf("%d%d",&in_s[i],&in_k[i]);
        
        in_s[i]--;
        in_k[i]--;
        
        if(cards_s[in_s[i]]==0){
            cards_s[in_s[i]]++;
            w--;
        }
        
        if(cards_k[in_k[i]]==0){
            cards_k[in_k[i]]++;
            h--;
        }
    }
    
    printf("%lld\n",(ll)W*H-(ll)w*h-n);
    
    return 0;
}