#include<bits/stdc++.h>
using namespace std;
using ll = long long;
using pll = pair<ll, ll>;
#define all(a) (a).begin(), (a).end()
#define pb push_back
#define fi first
#define se second
mt19937_64 rng(chrono::system_clock::now().time_since_epoch().count());
const ll MOD1000000007 = 1000000007;
const ll MOD998244353 = 998244353;
const ll MOD[3] = {999727999, 1070777777, 1000000007};
const ll LINF = 1LL << 60LL;
const int IINF = (1 << 30) - 1;


void solve(){
    int n, m; cin >> n >> m;
    vector<pair<int, ll>> C;
    ll ans = 0LL;
    for(int i=0; i<n; i++){
        ll c, d; cin >> c >> d;
        if(c == 0) ans += d;
        else C.push_back({c, d});
    }
    int MX = 25;
    vector<int> two(MX+1, 1);
    for(int i=1; i<=MX; i++) two[i] = two[i-1]*2;
    n = (int)C.size();
    vector<int> cnt(n, 0);
    for(int i=0; i<n; i++){
        while(C[i].fi*(cnt[i]+1) <= m) cnt[i]++;
    }
    sort(all(C), greater<pair<int, ll>>());
    vector<vector<ll>> dp(m+1, vector<ll>(MX+1, -1));
    dp[0][0] = 0;
    for(int i=0; i<n; i++){
        auto [c, d] = C[i];
        for(int j=m; j>=0; j--){
            for(int k=cnt[i]; k>=0; k--){
                if(j - c*two[k] >= 0) dp[j][k] = max(dp[j][k], dp[j - c*two[k]][k-1] + d);
            }
        }
    }
    
    ll sa = 0LL;
    for(int i=0; i<=m; i++) {
        for(int j=0; j<=MX; j++){
            if(dp[i][j] != -1) sa = max(sa, dp[i][j]);
        }
    }

    cout << sa + ans << '\n';
}

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    
    int T=1;
    //cin >> T;
    while(T--) solve();
}