#include <vector>
#include <algorithm>
#include <unistd.h>

struct IO {
  static const int bufsize=1<<21;
  char ibuf[bufsize], obuf[bufsize];
  char *ip, *op;
  IO(): ip(ibuf), op(obuf) { for(int t = 0, k = 0; (k = read(STDIN_FILENO, ibuf+t, sizeof(ibuf)-t)) > 0; t+=k); }
  ~IO(){ for(int t = 0, k = 0; (k = write(STDOUT_FILENO, obuf+t, op-obuf-t)) > 0; t+=k); }
  long long scan_int(){
    long long x=0;
    bool neg=false;
    for(;*ip<'+';ip++) ;
    if(*ip=='-'){ neg=true; ip++;}
    else if(*ip=='+'){ ip++;}
    for(;*ip>='0';ip++){
      x = 10*x+*ip-'0';
    }
    if(neg) x = -x;
    return x;
  }
  void put_int(long long x, char c=0){
    static char tmp[20];
    if(x==0){
      *op++ = '0';
    }
    else {
      int i;
      if(x<0){
        *op++ = '-';
        x = -x;
      }
      for(i=0; x; i++){
        tmp[i] = x % 10;
        x /= 10;
      }
      for(i--; i>=0; i--)
        *op++ = tmp[i]+'0';
    }
    if(c) *op++ = c;
  }
  void put_double(double x, char c=0){
    unsigned y;
    const int mask = (1<<24) - 1;
    put_int(x);
    *op++ = '.';
    x = x - (int) x;
    if(x < 0) x = -x;
    y = x * (1<<24);

    for(int i=0;i<7;i++){
      y *= 10;
      *op++ = '0' + (y>>24);
      y &= mask;
    }
  }
  inline char scan_char(){ return *ip++; }
  inline void put_char(char c){ *op++ = c; }
  inline char *scan_string(){ char *s = ip; while(*ip++!='\n'); *(ip-1)='\0'; return s;}
  inline void put_string(char *s, char c=0){ while(*s) *op++=*s++; if(c) *op++=c;}
};

typedef long long int ll;

struct state {
  ll aw;
  ll av;
  state(ll aw=0, ll av=0): aw(aw), av(av) {}
};

struct item {
  ll w;
  ll v;
  double d;
  item(ll w, ll v): w(w), v(v), d((double) v/w) { }
};
 
int n;
ll w;

ll lower;
 
std::vector<item> is;
std::vector<state> dp[2];
 
void add(const std::vector<state> &s, const item &k, std::vector<state> &u, ll uw){
  auto i = s.cbegin();
  auto j = s.cbegin();
  while(i != s.cend() && j != s.cend()){
    if(i->aw > uw){ i = s.cend(); break; }
    ll jav = j->av + k.v;
    ll jaw = j->aw + k.w;
    if(jaw > uw){ j = s.cend(); break; }
    if(i->aw <= jaw && i->av >= jav){ ++j; }
    else if(i->aw >= jaw && i->av <= jav){ ++i; }
    else if(i->aw < jaw){ u.push_back(*i++); }
    else { u.emplace_back(state(jaw, jav)); ++j;}
  }
  while(i != s.cend()){
    if(i->aw > uw) return;
    u.push_back(*i++);
  }
  while(j != s.cend()){
    ll jav = j->av + k.v;
    ll jaw = j->aw + k.w;
    if(jaw > uw) return;
    u.emplace_back(state(jaw, jav));
    ++j;
  }
}

void remove(const std::vector<state> &s, const item &k, std::vector<state> &u, ll uw){
  auto i = s.cbegin();
  auto j = s.cbegin();
  while(i != s.cend() && j != s.cend()){
    if(i->aw > uw){ i = s.cend(); break; }
    ll jav = j->av - k.v;
    ll jaw = j->aw - k.w;
    if(jaw > uw){ j = s.cend(); break; }
    if(i->aw <= jaw && i->av >= jav){ ++j; }
    else if(i->aw >= jaw && i->av <= jav){ ++i; }
    else if(i->aw < jaw){ u.push_back(*i++); }
    else { u.emplace_back(state(jaw, jav)); ++j;}
  }
  while(i != s.cend()){
    if(i->aw > uw) return;
    u.push_back(*i++);
  }
  while(j != s.cend()){
    ll jav = j->av - k.v;
    ll jaw = j->aw - k.w;
    if(jaw > uw) return;
    u.emplace_back(state(jaw, jav));
    ++j;
  }
}

ll upper;

 
inline void shrink(const std::vector<state> &s, double d0, double d1, std::vector<state> &u){
  for(auto x: s){
    ll t = (x.aw > w) ? x.av - (x.aw - w) * d0 : x.av + (w - x.aw) * d1;
    if(t >= lower) u.push_back(x);
    if(t > upper) upper = t;
  }
}

 
int main(){
  IO io;
  n = io.scan_int();
  w = io.scan_int();
  is.reserve(5000);
  dp[0].reserve(300);
  dp[1].reserve(300);

  is.emplace_back(item(1,0));

  for(int i=0;i<n;i++){
    ll ww, vv;
    vv = io.scan_int();
    ww = io.scan_int();
    if(ww <= w) is.emplace_back(item(ww,vv));
  }
  n = is.size()-1;

  std::sort(is.begin()+1, is.end(), [](const item &x, const item &y){ return  x.d > y.d; });
  is.emplace_back(item(1,0));


  ll aw = 0;
  ll av = 0;
  int ii;
  for(ii=1;ii<=n;ii++){
    const item &x = is[ii];
    if(aw + x.w > w) break;
    aw += x.w;
    av += x.v;
  }

  dp[0].emplace_back(state(aw, av));

  lower = av;
  ll sumw = w+aw;

  for(int i=ii-1, j=ii; i>0||j<=n; ){
    if(i>0){
      sumw -= is[i].w;
      remove(dp[0], is[i], dp[1], sumw);
      dp[0].resize(0);
      lower = (std::upper_bound(dp[1].cbegin(), dp[1].cend(), w, [](ll w, const state &x){ return x.aw > w; })-1)->av;
      shrink(dp[1], is[i-1].d, is[j].d, dp[0]);
      dp[1].resize(0);
      --i;
    }

    if(j<=n){
      add(dp[0], is[j], dp[1], sumw);
      dp[0].resize(0);
      lower = (std::upper_bound(dp[1].cbegin(), dp[1].cend(), w, [](ll w, const state &x){ return x.aw > w; })-1)->av;
      shrink(dp[1], is[i].d, is[j+1].d, dp[0]);
      dp[1].resize(0);
      ++j;
    }
    if(lower == upper) break;
  }

  lower = (std::upper_bound(dp[0].cbegin(), dp[0].cend(), w, [](ll w, const state &x){ return x.aw > w; })-1)->av;
  io.put_int(lower, '\n');
 
  return 0;
}