#include <bits/stdc++.h>
#include <sys/time.h>
using namespace std;
typedef signed long long ll;

#undef _P
#define _P(...) (void)printf(__VA_ARGS__)
#define FOR(x,to) for(x=0;x<(to);x++)
#define FORR(x,arr) for(auto& x:arr)
#define ITR(x,c) for(__typeof(c.begin()) x=c.begin();x!=c.end();x++)
#define ALL(a) (a.begin()),(a.end())
#define ZERO(a) memset(a,0,sizeof(a))
#define MINUS(a) memset(a,0xff,sizeof(a))
//-------------------------------------------------------

int N;
ll W;
pair<ll,ll> P[5050];
ll ma=0;

bool cmp(pair<ll,ll> L,pair<ll,ll> R) {
	return L.first*R.second<R.first*L.second;
}


void dfs(int cur,ll w,ll v) {
	ma=max(ma,v);
	if(cur==N) return;
	dfs(cur+1,w,v);
	if(w+P[cur].first<=W) dfs(cur+1,w+P[cur].first,v+P[cur].second);
}

void solve() {
	int i,j,k,l,r,x,y; string s;
	struct timeval start,end,ts;
	
	cin>>N>>W;
	FOR(i,N) cin>>P[i].second>>P[i].first;
	/*
	sort(P,P+N,cmp);
	reverse(P,P+N);
	dfs(0,0,0);
	*/
	
	srand(time(NULL));
	gettimeofday(&start,NULL);
	while(1) {
		gettimeofday(&end,NULL);
		ll span = (end.tv_sec - start.tv_sec)*1000000LL + (end.tv_usec - start.tv_usec);
		if(span>1500000) break;
		FOR(i,10) {
			random_shuffle(P,P+N);
			ll w=0,v=0;
			FOR(j,N) {
				if(w+P[j].first<=W) {
					w+=P[j].first;
					v+=P[j].second;
				}
			}
			ma=max(ma,v);
			
		}
		
	}
	
	cout<<ma<<endl;
	
}


int main(int argc,char** argv){
	string s;int i;
	if(argc==1) ios::sync_with_stdio(false), cin.tie(0);
	FOR(i,argc-1) s+=argv[i+1],s+='\n'; FOR(i,s.size()) ungetc(s[s.size()-1-i],stdin);
	cout.tie(0); solve(); return 0;
}