#include<bits/stdc++.h>
using namespace std;

long findMaxEfficiency(int m, vector<int> values, vector<int> resources) {
    int n = values.size();
	vector<int> order(n); 
	iota(order.begin(),order.end(),0);
	sort(order.begin(),order.end(), [&](const int& l, const int& r){
		return values[l] > values[r];
	});
	vector<vector<int>> dp0(n, vector<int> (m+1,0)), dp1(n, vector<int> (m+1,0));
    dp1[0][resources[order[0]]] = values[order[0]];
    for(int i=1; i<n; i++){
		for(int j=1; j<=m; j++){
			dp1[i][j] = dp1[i][j-1];
		    dp0[i][j] = max({dp0[i][j-1], dp0[i-1][j], dp1[i-1][j]});
			if(resources[order[i]] <= j) dp1[i][j] = max(dp1[i][j-1], values[order[i]] + max(dp0[i-1][j-resources[order[i]]], dp1[i-1][j-resources[order[i]]]));  	
	    }
	}	
	long ans = 0;
    for(int i=0; i<n; i++) ans = max(ans, 1L*values[order[i]]*dp1[i][m]);
	return ans;
}

int main(){
	int n,m; cin>>n>>m;
	vector<int> values(n), resources(n);
	for(int i=0; i<n; i++) cin>>values[i]>>resources[i];
	cout<<findMaxEfficiency(m,values,resources)<<"\n";
}