#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;

struct item{
    long value, weight;
};

int n;
long W;
vector<item> items;

long dp[5000][5000];

int mod_number_n[5001];
long mod_number_weight[5001];

long pack(int now, long weight_now){
    if(now == n){
        return 0;
    }else if(dp[now / mod_number_weight[n]][weight_now / ((W + mod_number_weight[n] - 1) / mod_number_weight[n] + 1)] != -1){
        return dp[now / mod_number_weight[n]][weight_now / ((W + mod_number_weight[n] - 1) / mod_number_weight[n] + 1)];
    }else{
        if(weight_now + items[now].weight > W){
            return dp[now / mod_number_weight[n]][weight_now / ((W + mod_number_weight[n] - 1) / mod_number_weight[n] + 1)] = pack(now + 1, weight_now);
        }else{
            return dp[now / mod_number_weight[n]][weight_now / ((W + mod_number_weight[n] - 1) / mod_number_weight[n] + 1)] = max(pack(now + 1, weight_now), items[now].value + pack(now + 1, weight_now + items[now].weight));
        }
    }
}

int main(){
    cin >> n >> W;
    items.resize(n);
    for(int i = 0; i < n; i++){
        cin >> items[i].value >> items[i].weight;
    }
    for(int i = 0; i < 5000; i++){
        for(int j = 0; j < 5000; j++){
            dp[i][j] = -1;
        }
    }
    for(int i = 0; i <= 5000; i++){
        mod_number_weight[i] = 3000;
    }
    mod_number_weight[500] = 2000;
    mod_number_weight[2000] = 4000;
    mod_number_weight[5000] = 3500;
    for(int i = 0; i <= 5000; i++){
        mod_number_n[i] = 1;
    }
    mod_number_n[5000] = 2;
    cout << pack(0, 0) << endl;
}