#include <cstdio>
#include <vector>
#include <algorithm>

int main(){
    int W, H, N;
    scanf("%d %d %d", &W, &H, &N);

    std::vector<int> mark(N), number(N);
    for(int i=0;i<N;i++){
        scanf("%d %d", &mark[i], &number[i]);
    }

    std::sort(mark.begin(), mark.end());
    mark.erase(std::unique(mark.begin(), mark.end()), mark.end());
    std::sort(number.begin(), number.end());
    number.erase(std::unique(number.begin(), number.end()), number.end());

    long long mn = mark.size(), nn = number.size(),
        res = mn * H + nn * W - mn * nn - N;
    
    printf("%lld\n", res);
}