题解

#include <bits/stdc++.h>
using namespace std;
int l,w,n;
struct qw{
	int x,y;
}e[5005];
bool cmp1(qw a,qw b){
	if(a.x == b.x){
        return a.y < b.y;
    }
	return a.x < b.x;
}
bool cmp2(qw a,qw b){
	if(a.y == b.y){
        return a.x < b.x;
    }
	return a.y > b.y;
}
int main(){
	cin >> l >> w >> n;
	if(!n){
		cout << l * w;
		return 0;
	}
	for(int i = 1;i <= n;i++){
		cin >> e[i].x >> e[i].y;
	}
	sort(e + 1,e + n + 1,cmp1);
	int ans = -1;
	for(int i = 1;i <= n;i++){
		int r = w,q = 0;
		for(int j = i + 1;j <= n;j++){
			ans = max(ans,(e[j].x - e[i].x) * (r - q));
			if(e[j].y >= e[i].y){
                r = min(r,e[j].y);
            }
            if(e[j].y <= e[i].y){
                q = max(q,e[j].y);
            }
		}
		ans = max(ans,(l - e[i].x) * (r - q));
	}
	for(int i = n;i >= 1;i--){
        int r = w,q = 0;
        for(int j = i - 1;j >= 1;j--){
            ans = max(ans,(e[i].x - e[j].x) * (r - q));
            if(e[j].y >= e[i].y){
                r =  min(r,e[j].y);
            }
            if(e[j].y <= e[i].y){
               q = max(q,e[j].y);  
            }
        }
        ans = max(ans,e[i].x * (r - q)); 
    }
	sort(e + 1,e + 1 + n,cmp2);
	for(int i = 1;i < n;i++){
		ans = max(ans,(e[i].y - e[i + 1].y) * l);
	}
	ans = max(ans,(w - e[1].y) * l);
	ans = max(ans,e[n].y * l);
	cout << ans;
    return 0;
}