#pragma GCC optimize ("O3")
#pragma GCC target ("avx")
#include "bits/stdc++.h" // define macro "/D__MAI"
 
using namespace std;
typedef long long int ll;
 
#define xprintf(fmt,...) fprintf(stderr,fmt,__VA_ARGS__)
#define debugv(v) {printf("L%d %s => ",__LINE__,#v);for(auto e:v){cout<<e<<" ";}cout<<endl;}
#define debugm(m) {printf("L%d %s is..\n",__LINE__,#m);for(auto v:m){for(auto e:v){cout<<e<<" ";}cout<<endl;}}
#define debuga(m,w) {printf("L%d %s is => ",__LINE__,#m);for(int x=0;x<(w);x++){cout<<(m)[x]<<" ";}cout<<endl;}
#define debugaa(m,w,h) {printf("L%d %s is..\n",__LINE__,#m);for(int y=0;y<(h);y++){for(int x=0;x<(w);x++){cout<<(m)[x][y]<<" ";}cout<<endl;}}
#define debugaar(m,w,h) {printf("L%d %s is..\n",__LINE__,#m);for(int y=0;y<(h);y++){for(int x=0;x<(w);x++){cout<<(m)[y][x]<<" ";}cout<<endl;}}
#define ALL(v) (v).begin(),(v).end()
#define repeat(cnt,l) for(auto cnt=0;cnt<(l);++cnt)
#define iterate(cnt,b,e) for(auto cnt=(b);cnt!=(e);++cnt)
#define MD 1000000007ll
#define PI 3.1415926535897932384626433832795
template<typename T1, typename T2>
ostream& operator <<(ostream &o, const pair<T1, T2> p) { o << "(" << p.first << ":" << p.second << ")"; return o; }
 
mt19937 mt(8901016);
inline int rand_int(int l, int h) {
    return uniform_int_distribution<>(l, h)(mt);
}
 
#ifdef __MAI
#define getchar_unlocked getchar
#define putchar_unlocked putchar
#endif
#ifdef __VSCC
#define getchar_unlocked _getchar_nolock
#define putchar_unlocked _putchar_nolock
#endif
namespace {
#define isvisiablechar(c) (0x21<=(c)&&(c)<=0x7E)
    class MaiScanner {
    public:
        template<typename T> void input_integer(T& var) {
            var = 0;
            T sign = 1;
            int cc = getchar_unlocked();
            for (; cc<'0' || '9'<cc; cc = getchar_unlocked())
                if (cc == '-') sign = -1;
            for (; '0' <= cc&&cc <= '9'; cc = getchar_unlocked())
                var = (var << 3) + (var << 1) + cc - '0';
            var = var*sign;
        }
        inline int c() { return getchar_unlocked(); }
        inline MaiScanner& operator>>(int& var) {
            input_integer<int>(var);
            return *this;
        }
        inline MaiScanner& operator>>(long long& var) {
            input_integer<long long>(var);
            return *this;
        }
        inline MaiScanner& operator>>(string& var) {
            int cc = getchar_unlocked();
            for (; !isvisiablechar(cc); cc = getchar_unlocked());
            for (; isvisiablechar(cc); cc = getchar_unlocked())
                var.push_back(cc);
        }
        template<typename IT> void in(IT begin, IT end) {
            for (auto it = begin; it != end; ++it) *this >> *it;
        }
    };
}
MaiScanner scanner;
 
 
 
 
ll n, cap;
pair<ll,ll> items[5010]; // <value, weight>
 
ll imos[5010];
 
ll best = 0;
 
 
 
void dfs(int index=0, ll value=0, ll weight=0) {
 
    if (cap < weight)
        return;
 
    if (index == n) {
        best = max(best, value);
        return;
    }
 
    ll value_lp = value;
    ll w = cap - weight;
    int i_g;
    for (i_g = index; i_g < n && 0 <= w - items[i_g].second; ++i_g) {
        w -= items[i_g].second;
        value_lp += items[i_g].first;
    }
 
    if (i_g == n || w == 0) {
        best = max(best, value_lp);
        return;
    }
 
    // 効率降順なので，これで抑えられる            
    double lp_opt = value_lp + items[i_g].first * ((w) / (double)items[i_g].second);
    if (lp_opt <= best) return;
 
    dfs(index + 1, value + items[index].first, weight + items[index].second);
    dfs(index + 1, value, weight);
}
 
 
void scan_testcase() {
 
    repeat(i, n) {
        ll v, w;
        scanner >> v >> w;
        items[i] = make_pair(v, w);
    }
}
 
void gen_testcase() {
 
    n = 100;
    cap = n * 30;
 
    repeat(i, n) {
        items[i] = make_pair(rand_int(1, 100), rand_int(1, 100));
    }
 
}
 
 
int main() {
    scanner >> n >> cap;
 
    scan_testcase();
    //gen_testcase();
 
    sort(items, items + n, [](auto& l, auto& r) {return l.first*r.second > r.first * l.second; });
    
    repeat(i, n) {
        imos[i + 1] = imos[i] + items[i].first;
    }
    dfs();
 
    cout << best << endl;
    
    return 0;
}