#include<iostream>
#include<vector>
#include<algorithm>
#include<cstring>
#include<cassert>
#include<cmath>
#include<ctime>
#include<iomanip>
#include<numeric>
#include<stack>
#include<queue>
#include<map>
#include<unordered_map>
#include<set>
#include<unordered_set>
#include<bitset>
#include<random>
using namespace std;
int N,M;
pair<int,int> VW[5000];
long long dp[2][5001];
void solve()
{
	cin >> N >> M;
	for(int i = 0;i < N;i++) cin >> VW[i].first >> VW[i].second;
	sort(VW,VW+N,greater<pair<int,int>>());
	int cur = 0;
	long long ans = -1;
	for(int i = 0;i < N;i++)
	{
		int nxt = 1-cur;
		for(int j = 0;j <= M;j++) dp[nxt][j] = -1;
		auto [v,w] = VW[i];
		for(int j = 0;j <= M;j++)
		{
			dp[nxt][j] = max(dp[nxt][j],dp[cur][j]);
			if(j+w <= M) dp[nxt][j+w] = max(dp[nxt][j+w],dp[cur][j]+v);
		}
		swap(cur,nxt);
		ans = max(ans,dp[cur][M]*v);
	}
	cout << ans << endl;
}
int main()
{
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int tt = 1;
	//cin >> tt;
	while(tt--) solve();
}