#include<iostream>
#include<cstdio>
#include<cmath>
#include<string>
#include<cstring>
#include<algorithm>
#include<cassert>
#include<stack>
#include<queue>
#include<vector>
#include<map>
#include<cstdlib>
using namespace std;
#define ll long long
#define ull unsigned long long
//#define int ll
int read()
{
	int now=0,nev=1; 
	char c=getchar();
	while(c<'0' || c>'9') 
	{ 
		if(c=='-') 
			nev=-1; 
		c=getchar();
	}
	while(c>='0' && c<='9') 
	{ 
		now=(now<<1)+(now<<3)+(c&15); 
		c=getchar(); 
	}
	return now*nev;
}
const int MAXN=1e6+10;
int n,m;
vector<int>v[MAXN],k[MAXN];
ll g[50][5010],f[50][5010];
int s;
void init()
{
	s=0;
	memset(f,0,sizeof(f));
	memset(g,0,sizeof(g));
	for(int i=0;i<=50;i++)
		v[i].clear(),k[i].clear();
}
int main()
{
	while(1)
	{
		n=read(),m=read();
		if(n==-1 && m==-1)
			break;
		init();
		for(int i=1;i<=n;i++)
		{
			int x,y;
			x=read(),y=read();
			int tt=0;
			while(((x>>tt)&1)==0)
				tt++;
			v[tt].push_back(y);
			k[tt].push_back(x>>tt); 
		}
		while(m>>s)
			s++;
		for(int i=0;i<=s;i++)
		{
			if(k[i].size()==0)
				continue;
			for(int j=0;j<k[i].size();j++)
			{
				for(int p=500;p>=k[i][j];p--)
					g[i][p]=max(g[i][p],g[i][p-k[i][j]]+v[i][j]);
			}
		}
		for(int i=0;i<=s;i++)
		{
			for(int j=500;j>=0;j--)
			{
				for(int p=0;p<=j;p++)
					f[i][j]=max(f[i][j],f[i-1][((j-p)<<1)+((m>>(i-1))&1)]+g[i][p]);
			}
		}
		printf("%lld\n",f[s-1][1]);
	}
	return 0;
}