昨天一遍AC，今天重新敲了一遍20分了（doge） 求dalao指点，今天写的代码附上

#include<bits/stdc++.h>
#define ll long long
#define MAX  pow(10,9)+1
using namespace std;
struct jx
{
	ll x1,y1,x2,y2;	
};
jx a[2*100000];
ll max_x=-MAX,min_x=MAX,max_y=-MAX,min_y=MAX;
int main(){
	int n;
	cin>>n;
	for(int i=0;i<n;i++)
	{
		cin>>a[i].x1>>a[i].y1>>a[i].x2>>a[i].y2;
		if(max_x<a[i].x1) max_x=a[i].x1;
		if(min_x>a[i].x1) min_x=a[i].x1;
		if(max_x<a[i].x2) max_x=a[i].x2;
		if(min_x>a[i].x2) min_x=a[i].x2;
		if(max_x<a[i].y1) max_y=a[i].y1;
		if(min_x>a[i].y1) min_y=a[i].y1;
		if(max_x<a[i].y2) max_y=a[i].y2;
		if(min_x>a[i].y2) min_y=a[i].y2;
	}
	cout<<(max_x-min_x)*(max_y-min_y);
	return 0;
}