import java.io.*;
import java.util.*;


class Main {
    public static void main(String[] args) {
        MyScanner sc = new MyScanner();
        out = new PrintWriter(new BufferedOutputStream(System.out));
        int n=sc.nextInt();
        long ww=sc.nextLong();
        int U=64;
        int W=5001*U;
        long D=Math.max(1,ww/U/n);
        long[]v=new long[n],w=new long[n];
        int[]vt=new int[n];
        for(int i=0;i<n;++i){
            v[i]=sc.nextInt();
            w[i]=sc.nextInt();
            vt[i]=w[i]>ww?W:(int)((w[i]+D-1)/D);
        }
        long[]dp=new long[W];
        Arrays.fill(dp,0);
        for(int i=0;i<n;++i){
            for(int j=W-1;j>=vt[i];--j)
                dp[j]=Math.max(dp[j],dp[j-vt[i]]+v[i]);
        }
        long ans=0;
        for(int i=0;i<W&&i*D<=ww;++i)ans=Math.max(ans,dp[i]);
        out.println(ans);
        out.close();
    }
    // http://codeforces.com/blog/entry/7018
    //-----------PrintWriter for faster output---------------------------------
    public static PrintWriter out;
    //-----------MyScanner class for faster input----------
    public static class MyScanner {
        BufferedReader br;
        StringTokenizer st;
        public MyScanner() {
            br = new BufferedReader(new InputStreamReader(System.in));
        }
        String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }
        int nextInt() {
            return Integer.parseInt(next());
        }
        long nextLong() {
            return Long.parseLong(next());
        }
        double nextDouble() {
            return Double.parseDouble(next());
        }
        String nextLine(){
            String str = "";
            try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }
    }
}