#include <iostream>
#include <fstream>
#include <algorithm>
using namespace std;
ifstream f("rucsac.in");
ofstream g("rucsac.out");
struct rucsac
{
    int gre,val,cas;
} x[5001];

int main()
{
    int n,G,i,t=0,s=0;
    f>>n>>G;
    for(i=1; i<=n; i++)
    {
        f>>x[i].gre>>x[i].val;
        x[i].cas=x[i].val-x[i].gre;
    }
    rucsac aux;
    while(t==0)
    {
        t=1;
        for(i=1; i<n; i++)
            if(x[i].cas<x[i+1].cas)
            {
                aux=x[i];
                x[i]=x[i+1];
                x[i+1]=aux;
                t=0;
            }
    }
    for(i=1; i<=n; i++)
        if(G-x[i].gre>=0)
        {
            s=s+x[i].val;
            G=G-x[i].gre;
        }
    g<<s;

    return 0;
}