#include<bits/stdc++.h>
#define REP(i,n) for(int i=0,i##_len=(n);i<i##_len;++i)
#define rep(i,a,b) for(int i=int(a);i<int(b);++i)
#define All(x) (x).begin(),(x).end()
using namespace std;
typedef long long ll;

int main(){
    ll W,H,N;cin>>W>>H>>N;
    vector<ll> mark(W),fig(H,0);
    REP(i,N){
        ll S,K;cin>>S>>K;
        S--;K--;
        mark[S]++;
        fig[K]=1;
    }
    ll f=0;
    REP(i,H) f+=fig[i];
    ll ans=0;
    REP(i,W){
        if(mark[i]>0){
            ans+=H-mark[i];
        }
        else{
            ans+=f;
        }
    }
    cout<<ans<<endl;
}