#include <bits/stdc++.h>

using namespace std;

struct pizza{
    int p;
    int d;
};

unsigned long xor128(){
    static unsigned long x = 123456789, y = 362436069, z = 521288629, w = 88675123;
    unsigned long t = (x ^ (x << 11));
    x = y;
    y = z;
    z = w;
    return (w = (w ^ (w >> 19)) ^ (t ^ (t >> 8)));
}

int main(){
    int n, k;
    cin >> n >> k;
    vector<pizza> v(n);
    for(int i = 0; i < n; i++){
        cin >> v[i].p >> v[i].d;
    }
    sort(v.begin(), v.end(), [](pizza &l, pizza &r){
        return l.p < r.p;
    });

    int ans = 0;
    int trial = 5000, get = 5000;
    for(int t = 0; t < trial; t++){
        vector<int> used(n, false);
        int now = 0;
        int tmp = 0;
        for(int i = 0; i < get; i++){
            int nxt = xor128() % n;
            if(!used[nxt] && v[nxt].p + now <= k){
                now += v[nxt].p;
                tmp += v[nxt].d;
                used[nxt] = true;
            }
        }
        priority_queue<int> q;
        for(int i = 0; i < n; i++){
            if(used[i]){
                if(!q.empty()){
                    tmp += q.top();
                    q.pop();
                }
            }else{
                q.push(v[i].d);
            }
        }
        ans = max(ans, tmp);
    }
    cout << ans << endl;
}