#include<bits/stdc++.h>

using namespace std;
typedef unsigned int uint;
typedef long long int ll;
typedef unsigned long long int ull;

#define debugv(v) printf("L%d %s => ",__LINE__,#v);for(auto e:v){cout<<e<<" ";}cout<<endl;
#define debugm(m) printf("L%d %s is..\n",__LINE__,#m);for(auto v:m){for(auto e:v){cout<<e<<" ";}cout<<endl;}
#define debuga(m,w) printf("L%d %s is => ",__LINE__,#m);for(int x=0;x<(w);x++){cout<<(m)[x]<<" ";}cout<<endl;
#define debugaa(m,w,h) printf("L%d %s is..\n",__LINE__,#m);for(int y=0;y<(h);y++){for(int x=0;x<(w);x++){cout<<(m)[x][y]<<" ";}cout<<endl;}
#define debugaar(m,w,h) printf("L%d %s is..\n",__LINE__,#m);for(int y=0;y<(h);y++){for(int x=0;x<(w);x++){cout<<(m)[y][x]<<" ";}cout<<endl;}
#define ALL(v) (v).begin(),(v).end()
#define BIGINT 0x7FFFFFFF
#define E107 1000000007ll
void printbit(int u){if(u==0)cout<<0;else{int s=0,k=0;for(;0<u;u>>=1,k++)s=(s<<1)|(u&1);for(;0<k--;s>>=1)cout<<(s&1);}}

#define TIME chrono::system_clock::now()
#define MILLISEC(t) (chrono::duration_cast<chrono::milliseconds>(t).count())

namespace{
    std::chrono::system_clock::time_point t;
    void tic(){t=TIME;}
    void toc(){fprintf(stderr,"TIME : %lldms\n",MILLISEC(TIME-t));}
}

template<typename T1,typename T2>
ostream& operator <<(ostream &o,const pair<T1,T2> p){o<<"("<<p.first<<":"<<p.second<<")";return o;}

int width,height;
int m,n;
int nx,ny;

map<int,int> sumx;
map<int,int> sumy;

int main(){
    int i,j,k;
    int x,y,a,b;
    
    cin >> width >> height >> n;
    nx=ny=1;
    
    for (i=0;i<n;++i){
        scanf("%d%d",&x,&y);
        if (sumx.count(x)){
            sumx[x] && --sumx[x];
        }else{
            sumx[x] = width-nx;
            nx=min(++nx,width);
        }
        if (sumy.count(y)){
            sumy[y] && --sumy[y];
        }else{
            sumy[y] = height-ny;
            ny=min(++ny,height);
        }
    }
    
    ll result=0;
    for (auto p : sumx){
        result+=p.second;
    }
    for (auto p : sumy){
        result+=p.second;
    }
    cout << result << endl;
    

    return 0;
}