typedef long long ll;
typedef long double ld;
#include <bits/stdc++.h>
using namespace std;
#define int long long

signed main(){
    ll n,m;
    std::cin >> n>>m;
    vector<pair<ll,ll>> vw(n);
    for (int i = 0; i < n; i++) {
        std::cin >> vw[i].first >> vw[i].second;
    }
    sort(vw.rbegin(),vw.rend());
    vector<vector<ll>> dp(n+1, vector<ll>(m+1,-1));
    ll ans = 0;
    dp[0][0] = 0;
    for (int i = 0; i < n; i++) {
        for (int j = 0; j <= m; j++) {
            dp[i+1][j] = dp[i][j];
            
            if(j-vw[i].second>=0){
                dp[i+1][j] = dp[i][j-vw[i].second]+vw[i].first;
                ans = max(ans, dp[i+1][j]*vw[i].first);
            }
        }
    }
    std::cout << ans << std::endl;
}