#include <bits/stdc++.h>
using namespace std;
int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int N, M;
    cin >> N >> M;
    vector<pair<int, long long>> cards;
    long long sumZero = 0;
    for(int i = 0; i < N; i++){
        int c;
        long long d;
        cin >> c >> d;
        if(c == 0) sumZero += d;
        else cards.push_back({c, d});
    }
    sort(cards.begin(), cards.end(), [](auto &a, auto &b){
        return a.first > b.first;
    });
    int maxK = min((int)cards.size(), 10);
    const int cap = M;
    const long long NEG = -1LL << 60;
    vector<vector<long long>> dp(maxK+1, vector<long long>(cap+1, NEG));
    dp[0][0] = 0;
    for(auto &card : cards){
        int c = card.first;
        long long d = card.second;
        for(int k = maxK - 1; k >= 0; k--){
            int mul = 1 << k;
            for(int e = 0; e <= cap; e++){
                if(dp[k][e] == NEG) continue;
                int ne = e + mul * c;
                if(ne <= cap) dp[k+1][ne] = max(dp[k+1][ne], dp[k][e] + d);
            }
        }
    }
    long long ans = 0;
    for(int k = 0; k <= maxK; k++){
        for(int e = 0; e <= cap; e++){
            ans = max(ans, dp[k][e]);
        }
    }
    cout << ans + sumZero << "\n";
    return 0;
}