1 #include<stdio.h>
 2 #include<string.h>
 3 #include<algorithm>
 4 using namespace std;
 5 template<class T>void read(T &x){
 6     int f=0;x=0;char ch=getchar();
 7     while(ch<'0'||ch>'9')  {f|=(ch=='-');ch=getchar();}
 8     while(ch>='0'&&ch<='9'){x=(x<<1)+(x<<3)+(ch^48);ch=getchar();}
 9     x=f?-x:x;
10 }
11
12 const int N=5007;
13 int ans,yx,yn,n,l,w,lst;
14 bool qwq[30007];
15 struct yhhh{
16     int x,y;
17 }a[N];
18
19 inline bool cmp(yhhh A,yhhh B){
20     return A.x<B.x;
21 }
22
23 int main(){
24     read(l),read(w),read(n);
25     for(int i=1;i<=n;++i)
26         read(a[i].x),read(a[i].y),qwq[a[i].y]=1;
27     for(int i=0;i<=w;++i)
28         if(qwq[i]){
29             ans=max(ans,w*(i-lst));
30             lst=i;
31         }
32     ans=max(ans,w*(w-lst));
33     a[++n].x=0,a[n].y=0;
34     a[++n].x=l,a[n].y=0;
35     a[++n].x=0,a[n].y=w;
36     a[++n].x=l,a[n].y=w;
37     sort(a+1,a+n+1,cmp);
38     for(int i=1;i<=n;++i){
39         yn=0,yx=w;
40         for(int j=i+1;j<=n;++j){
41             if(yx<=yn) break;
42             if(a[j].y>yx||a[j].y<yn) continue;
43             ans=max(ans,(a[j].x-a[i].x)*(yx-yn));
44             if(a[j].y>=a[i].y) yx=min(yx,a[j].y);
45             if(a[j].y<=a[i].y) yn=max(yn,a[j].y);
46         }
47         ans=max(ans,(yx-yn)*(l-a[i].x));
48     }
49     for(int i=n;i>=1;--i){
50         yn=0,yx=w;
51         for(int j=i-1;j>=1;--j){
52             if(yx<=yn) break;
53             if(a[j].y>yx||a[j].y<yn) continue;
54             ans=max(ans,(a[i].x-a[j].x)*(yx-yn));
55             if(a[j].y>=a[i].y) yx=min(yx,a[j].y);
56             if(a[j].y<=a[i].y) yn=max(yn,a[j].y);
57         }
58     }
59     printf("%d\n",ans);
60     return 0;
61 } 

ans=max(ans,(a[j].x-a[i].x)*(yx-yn));