题号 $\text{P6785}$ 记录 $\text{R159681403}$ thx for help!

#include <bits/stdc++.h>
using namespace std;
int t[2000033];
int main(){
	int n, k; cin >> n >> k;
	int x = 0;
	for(int i = 1; i <= n; ++ i){
		int a, b; cin >> a >> b;
		t[a]+=b; x=max(x,a);
	}
	int ans = -1;
	if(k == 0){
		for(int i = 0; i <= x; ++ i){
			if(t[i] > 1){
				ans = max(ans, i * t[i]);
			}
		}
		if(ans == -1){
			cout << "NO";
		} else{
			cout << ans;
		}
		return 0;
	}
	for(int i = 0; i <= x; ++i){
		if(t[i] && t[i + k]){
			ans = max(ans, min(t[i], t[i + k]) * (2 * i + k));
		}
	}
	if(ans == -1){
		cout << "NO";
	} else{
		cout << ans;
	}
	return 0;
}