using System;
using System.Collections.Generic;
using System.Collections;
using System.Collections.Specialized;
using System.Linq;
using System.Text;
using System.IO;
using System.Reflection;
using static System.Math;
using System.Numerics;
static class Program{
	const int mod=(int)1e9+7;
	static void Main(){
		Sc sc=new Sc();
		var s=sc.La;
		var a=sc.Arr((int)s[0],()=>sc.La);
		int n=(int)s[0]/2;
		int m=1<<n;
		var h1=new long[m-1][];
		for(int i = 1;i<m;i++) {
			h1[i-1]=new long[2];
			for(int j = 0;(1<<j)<=i;j++) {
				if((i&(1<<j))!=0){
					h1[i-1][0]+=a[j][0];
					h1[i-1][1]+=a[j][1];
				}
			}
		}
		if(s[0]%2==1){m<<=1;}
		var h2=new long[m-1][];
		for(int i = 1;i<m;i++) {
			h2[i-1]=new long[2];
			for(int j = 0;(1<<j)<=i;j++) {
				if((i&(1<<j))!=0){
					h2[i-1][0]+=a[j+n][0];
					h2[i-1][1]+=a[j+n][1];
				}
			}
		}
		Array.Sort(h1,(u,v)=>u[1].CompareTo(v[1]));
		Array.Sort(h2,(u,v)=>u[1].CompareTo(v[1]));
		long ans=h2[0][1]<=s[1]?h2[0][0]:0;
		for(int i = 1;i<h2.Length;i++) {
			if(h2[i][1]<=s[1]){ans=Max(ans,h2[i][0]);}
			if(h2[i-1][0]>h2[i][0]){h2[i][0]=h2[i-1][0];}
		}
		for(int i = 0;i<h1.Length;i++) {
			if(h1[i][1]==s[1]){ans=Max(ans,h1[i][0]);}
			else if(h1[i][1]<s[1]){
				int p=h2.Bs(s[1]-h1[i][1]+1,true);
				ans=Max(ans,h1[i][0]+(p==-1?0:h2[p][0]));
			}
		}
		Console.WriteLine("{0}",ans);
	}
}
static class Ex1{
	public static int Bs(this long[][] a,long x,bool b){return Bs2(a,x,true,a.Length);}
	private static int Bs2(long[][] a,long x,bool b,int ub){
		int lb=-1,mid=0;
		while(ub-lb>1){
			mid=(ub+lb)/2;
			if(a[mid][1]>=x){ub=mid;}
			else{lb=mid;}
		}
		return b?lb:ub;
	}
}

public class Sc{
	public int I{get{return int.Parse(Console.ReadLine());}}
	public long L{get{return long.Parse(Console.ReadLine());}}
	public double D{get{return double.Parse(Console.ReadLine());}}
	public string S{get{return Console.ReadLine();}}
	public int[] Ia{get{return Array.ConvertAll(Console.ReadLine().Split(),int.Parse);}}
	public long[] La{get{return Array.ConvertAll(Console.ReadLine().Split(),long.Parse);}}
	public double[] Da{get{return Array.ConvertAll(Console.ReadLine().Split(),double.Parse);}}
	public string[] Sa{get{return Console.ReadLine().Split();}}
	public object[] Oa{get{return Console.ReadLine().Split();}}
	public int[] Ia2{get{return Array.ConvertAll(("0 "+Console.ReadLine()+" 0").Split(),int.Parse);}}
	public int[] Ia3(int a){return Array.ConvertAll((a.ToString()+" "+Console.ReadLine()).Split(),int.Parse);}
	public int[] Ia3(bool a,int b,bool c,int d){return Array.ConvertAll(((a?b.ToString()+" ":"")+Console.ReadLine()+(c?" "+d.ToString():"")).Split(),int.Parse);}
	public long[] La2{get{return Array.ConvertAll(("0 "+Console.ReadLine()+" 0").Split(),long.Parse);}}
	public long[] La3(int a){return Array.ConvertAll((a.ToString()+" "+Console.ReadLine()).Split(),long.Parse);}
	public long[] La3(bool a,int b,bool c,int d){return Array.ConvertAll(((a?b.ToString()+" ":"")+Console.ReadLine()+(c?" "+d.ToString():"")).Split(),long.Parse);}
	public T[] Arr<T>(int n,Func<T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f();}return a;}
	public T[] Arr<T>(int n,Func<int,T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f(i);}return a;}
	public T[] Arr<T>(int n,Func<string[],T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f(Console.ReadLine().Split());}return a;}
	public T[] Arr<T>(int n,Func<int,string[],T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f(i,Console.ReadLine().Split());}return a;}
}


Measured memory_bytes: 140124