#include<bits/stdc++.h>
using namespace std;
const int MAXN=30001;
int best=0,v,m,n,costw[MAXN]={0},value[MAXN]={0};;
int to_try(int i,int cur_w,int cur_v)
{ 
	if(i>n)
	{
		if(cur_w<=m)
		{
			if(cur_v>best)
				best=cur_v;
		}
		return 0;
	}
	else 
	{
		for(int k=0;k<=1;k++)
		{
			if(cur_w+costw[i]*k<=m) 
				to_try(i+1,cur_w+costw[i]*k,cur_v+value[i]*k);
		}
	}
}
int main(){
	freopen("delicious.in","r",stdin);
	freopen("delicious.out","w",stdout);
	cin>>n>>m;
	for(int i=1;i<=n;i++) cin>>costw[i]>>value[i];
	to_try(1,0,0);
	cout<<best<<endl; 
	return 0;
}