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T1

堆优化，枚举删除数量贪心。

#include <algorithm>
#include <iostream>
#include <cstring>
#include <cstdio>
#include <queue>
#define N 1111111
#define LL long long

using namespace std;
struct BLO{
	LL x,y;
	int id;
	friend bool operator < (const BLO &a,const BLO &b){
		return a.y>b.y;
	}
};
priority_queue<BLO>yq;
BLO arr[N];
int pn,dn;
bool isd[N];
LL ans=0;
int main(){
//	freopen("data/d2.in","r",stdin);\
	freopen("d.out","w",stdout);
	int T;
	scanf("%d",&T);
	while(T--){
		while(!yq.empty())yq.pop();
		ans=0;
		scanf("%d%d",&pn,&dn);
		for(int i=1;i<=pn;i++){
			scanf("%lld%lld",&arr[i].x,&arr[i].y);
			arr[i].id=i;
		}
		sort(arr+1,arr+pn+1,[](const BLO &a,const BLO &b){return a.x<b.x;});
		for(int i=dn+1;i<=pn;i++)
			yq.push(arr[i]);
		for(int i=dn;i>=0;i--){
			ans=max(ans,yq.top().y*arr[i+1].x);
			if(arr[i].y>yq.top().y){
				yq.pop();
				yq.push(arr[i]);
			}
		}
		printf("%lld\n",ans);
	}
}