#include<cstdio>
#include<iostream>
#include<cstdlib>
#include<cstring>
#include<string>
#include<algorithm>
#include<map>
#include<queue>
#include<vector>
#include<cmath>
#include<utility>
using namespace std;
typedef long long LL;
typedef long double LD;

const int N = 108, INF = 0x3F3F3F3F, EPS = 0.4;

struct data{
	LL w, val;
	bool operator<(const data &tp)const{
		return val * tp.w > tp.val * w;
	}

}pk[N];


int n;
LL sum[N], sw[N], lim;
LL ans;

void dfs(int d, LL w, LL val){
	if(val > ans){
		ans =  val;
	}
	if(d >= n){
		return;
	}
	if(val + (LD)pk[d].val / (LD)pk[d].w * (lim - w) + EPS <= ans){
        return;
	}

	if(w + pk[d].w <= lim){
		dfs(d + 1, w + pk[d].w, val + pk[d].val);
	}
	dfs(d + 1, w, val);

}

int main(){
    while(~scanf("%d %I64d", &n, &lim)){
    	for(int i = 0; i < n; i++){
    		scanf("%I64d %I64d", &pk[i].w, &pk[i].val);
    	}
    	sort(pk, pk + n);
    	ans = 0;
    	sum[n] = 0;
    	sw[n] = 0;
    	dfs(0, 0, 0);
    	printf("%I64d\n", ans);

    }
    return 0;
}