#include<stdio.h>
int WF[1000000];
int HF[1000000];
main(){
    int W,H,N;
    scanf("%d%d%d",&W,&H,&N);
    int wc = 0;
    int hc = 0;
    for(int i = 0;i < N;i++){
        int a,b;
        scanf("%d%d",&a,&b);
        if(!WF[a-1]){
            wc++;
            WF[a-1]++;
        }
        if(!HF[b-1]){
            hc++;
            HF[b-1]++;
        }
    }
    long long ans = (long long)(W*H - (W-wc)*(H-hc) - N);
    printf("%lld\n",ans);
}