import std.conv, std.stdio, std.string;
import std.algorithm, std.array, std.bigint, std.container, std.math, std.numeric, std.range, std.regex, std.typecons;
import core.bitop;

class EOFException : Throwable { this() { super("EOF"); } }
string[] tokens;
string readToken() { for (; tokens.empty; ) { if (stdin.eof) { throw new EOFException; } tokens = readln.split; } auto token = tokens.front; tokens.popFront; return token; }
int readInt() { return readToken.to!int; }
long readLong() { return readToken.to!long; }
real readReal() { return readToken.to!real; }

void chmin(T)(ref T t, in T f) { if (t > f) t = f; }
void chmax(T)(ref T t, in T f) { if (t < f) t = f; }

int binarySearch(T)(in T[] as, in bool delegate(T) test) { int low = -1, upp = cast(int)(as.length); for (; low + 1 < upp; ) { int mid = (low + upp) >> 1; (test(as[mid]) ? low : upp) = mid; } return upp; }
int lowerBound(T)(in T[] as, in T val) { return as.binarySearch((T a) => (a < val)); }
int upperBound(T)(in T[] as, in T val) { return as.binarySearch((T a) => (a <= val)); }


// ap / aq < bp / bq
bool compare(long ap, long aq, long bp, long bq) {
  return ((ap / aq != bp / bq) ? (ap / aq < bp / bq) : (ap % aq * bq < bp % bq * aq));
}

int N;
long W;
Tuple!(long, "v", long, "w")[] P;

long[] sumV, sumW;
long ans;

void dfs(int i, long v, long w) {
  const j = sumW.upperBound(sumW[i] + (W - w)) - 1;
  const greedy = v + (sumV[j] - sumV[i]);
  chmax(ans, greedy);
  // ans >= greedy + (P[j].v / P[j].w) * (W - w - (sumW[j] - sumW[i]))
  if (j == N || !compare(ans - greedy, P[j].v, W - w - (sumW[j] - sumW[i]), P[j].w)) {
    return;
  }
  if (w + P[i].w <= W) {
    dfs(i + 1, v + P[i].v, w + P[i].w);
  }
  dfs(i + 1, v, w);
}

void main() {
  try {
    for (; ; ) {
      N = readInt();
      W = readLong();
      P.length = N;
      foreach (i; 0 .. N) {
        P[i].v = readLong();
        P[i].w = readLong();
      }
      
      // a.v / a.w > b.v / b.w
      P.sort!((a, b) => compare(b.v, b.w, a.v, a.w));
      
      sumV = new long[N + 1];
      sumW = new long[N + 1];
      foreach (i; 0 .. N) {
        sumV[i + 1] = sumV[i] + P[i].v;
        sumW[i + 1] = sumW[i] + P[i].w;
      }
      
      ans = 0;
      dfs(0, 0, 0);
      writeln(ans);
    }
  } catch (EOFException e) {
  }
}