#include <iostream>
#include <fstream>
using namespace std;
int n,gr,i,ok;
float aux,c[5001],g[5001],p[5001],castig,nr,cmax;
ifstream in("rucsac.in");
ofstream out("rucsac.out");
int main()
{
    in>>n;
    in>>gr;
    for(i=1;i<=n;i++)
    {
        in>>g[i];
        in>>c[i];
        p[i]=c[i]/g[i]*c[i];
    }
    do
    {
        ok=0;
        for(i=1;i<n;i++)
        {
            if(p[i]<p[i+1])
            {
                aux=c[i];c[i]=c[i+1];c[i+1]=aux;
                aux=g[i];g[i]=g[i+1];g[i+1]=aux;
                aux=p[i];p[i]=p[i+1];p[i+1]=aux;
                ok=1;
            }
        }
    }while(ok==1);
    i=0;castig=0;nr=1;
    while (gr>0&&i<n&&nr==1)
    {
        i++;
        if(g[i]<=gr)
        {
            gr=gr-g[i];
            castig=castig+c[i];
        }
        else
        {
            nr=0;
        }
    }
    cmax=castig;
    while(i<n)
    {
        if(gr!=0)
        {
        gr=gr+g[i];
        castig=castig-c[i];
        i++;
        if(gr>=g[i])
        {
            gr=gr+g[i];
            castig=castig+c[i];
            if(cmax<castig)
                cmax=castig;
        }
        }
        else
            i=n;
    }
    out<<cmax;
}