#pragma GCC optimize("Ofast")
#include <iostream>
#include <vector>
#include <algorithm>
#include <map>
#include <queue>
#include <cstdio>
#include <ctime>
#include <assert.h>
#include <chrono>
#include <random>
#include <numeric>
#include <set>
#include <deque>
#include <stack>
#include <sstream>
#include <utility>
#include <cstring>
#include <unordered_map>
#include <unordered_set>
#include <tuple>
#include <array>
#include <bitset>
using namespace std;
typedef long long int ll;
typedef unsigned long long ull;

mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
ll myRand(ll B) {
    return (ull)rng() % B;
}
inline double time() {
    return static_cast<long double>(chrono::duration_cast<chrono::nanoseconds>(chrono::steady_clock::now().time_since_epoch()).count()) * 1e-9;
}

ll dp[5001][5001];

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    ll res = 0;
    int n,m; cin >> n >> m;
    vector<pair<int,int>> v(n);
    for(int i=0;i<n;i++){
        cin >> v[i].first >> v[i].second;
    }
    sort(v.rbegin(), v.rend());
    for(int i=0;i<=n;i++){
        for(int j=0;j<=m;j++){
            dp[i][j] = -1;
        }
    }    
    dp[0][0] = 0;
    for(int i=0;i<n;i++){
        for(int j=0;j<=m;j++){
            if(dp[i][j] == -1)continue;
            // 使わない
            dp[i+1][j] = max(dp[i+1][j], dp[i][j]);
            // 使う
            if(j+v[i].second <= m){
                res = max(res, (ll)v[i].first*(ll)(dp[i][j]+v[i].first));
                dp[i+1][j+v[i].second] = max(dp[i+1][j+v[i].second], dp[i][j]+v[i].first);
            }
        }
    }
    cout << res << endl;
}