#include <bits/stdc++.h>
using namespace std;
long long n ,k , a[1000005] , cnt[1000005];
bool vis[1000005];
int main () {
	cin >> n >> k;
	for(long long i = 1;i <= n;i ++){
		long long f;
		cin >> a[i] >> f;
		cnt[a[i]] += f;
	}
	sort(a + 1 , a + 1 +n);
	long long sum = 1e9;
	for(long long i = 1;i <= n - k;i ++){
		if(cnt[a[i]+k] != 0 && cnt[a[i]] != 0){
			sum = min(cnt[a[i]],cnt[a[i]+k])*(a[i]+a[i]+k);
		}
	}
	if(sum == 1e9){
		cout << "NO";
	}else
		cout << sum;
	return 0;
}
 

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