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31 lines
770 B
C++

#define _CRT_SECURE_NO_WARNINGS
#define _SILENCE_CXX17_C_HEADER_DEPRECATION_WARNING
#include <bits/stdc++.h>
using namespace std;
int main()
{
ios::sync_with_stdio(false);
int n, k;
cin >> n >> k;
vector<pair<int64_t, int64_t>> v(n);
for (auto &p : v) cin >> p.second >> p.first;
sort(begin(v), end(v));
reverse(begin(v), end(v));
long long res = 0, sum = 0;
multiset<int64_t> s;
for (int i = 0; i < n; i++)
{
s.insert(v[i].second);
sum += v[i].second;
while (s.size() > k)
{
auto it = s.begin();
sum -= *it;
s.erase(s.begin());
}
res = max(res, sum * v[i].first);
}
cout << res << endl;
return 0;
}