import std.conv, std.functional, std.range, std.stdio, std.string;
import std.algorithm, std.array, std.bigint, std.bitmanip, std.complex, std.container, std.math, std.mathspecial, std.numeric, 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; }

string COLOR(string s = "") { return "\x1b[" ~ s ~ "m"; }

bool chmin(T)(ref T t, in T f) { if (t > f) { t = f; return true; } else { return false; } }
bool chmax(T)(ref T t, in T f) { if (t < f) { t = f; return true; } else { return false; } }

int binarySearch(alias pred, T)(in T[] as) { int lo = -1, hi = cast(int)(as.length); for (; lo + 1 < hi; ) { const mid = (lo + hi) >> 1; (unaryFun!pred(as[mid]) ? hi : lo) = mid; } return hi; }
int lowerBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a >= val)); }
int upperBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a > val)); }


long[string] cache;
long brute(long K, long[] A) {
  A.sort;
  const key = A.to!string;
  auto ptr = key in cache;
  if (ptr) return *ptr;
  long ret;
  
  const N = cast(int)(A.length);
  if (N) {
    ret = long.min;
    foreach (i; 0 .. N) {
      if (A[i] <= K) {
        chmax(ret, A[i] - brute(K, A[0 .. i] ~ A[i + 1 .. N]));
      } else {
        foreach (b; 1 .. A[i]) {
          chmax(ret, 0 - brute(K, A[0 .. i] ~ [b, A[i] - b] ~ A[i + 1 .. $]));
        }
      }
    }
  }
  
  return cache[key] = ret;
}

long solve(long K, long[] A) {
  A.sort;
  const N = cast(int)(A.length);
  const cut = A.upperBound(K);
  long ans;
  foreach (i; 0 .. cut) {
    ans += (i&1?-1:+1) * A[cut - 1 - i];
  }
  int sig = (cut&1?-1:+1);
  foreach (i; cut .. N) if (!(A[i] & 1)) {
    sig = -sig;
  }
  foreach (i; cut .. N) if (A[i] & 1) {
    ans += sig * (-1);
    sig = -sig;
  }
  return ans;
}

void main() {
  debug {{
    foreach (K; 1L .. 5L + 1) {
      cache.clear;
      writeln("K = ", K);
      foreach (a; 1L .. 10L + 1) {
        writeln([a], ": ", brute(K, [a]));
      }
      foreach (m; 1 .. 10) {
        foreach (p; 0 .. 1 << (m-1)) {
          long[] bs;
          bs ~= 0;
          foreach (j; 1 .. m) if (p >> (j-1) & 1) bs ~= j;
          const N = cast(int)(bs.length);
          bs ~= m;
          auto A = new long[N];
          foreach (i; 0 .. N) A[i] = bs[i + 1] - bs[i];
          const brt = brute(K, A);
          const slv = solve(K, A);
          assert(brt == slv, format("%s %s: %s %s", K, A, brt, slv));
        }
      }
      writeln;
    }
  }}
  
  try {
    for (; ; ) {
      const N = readInt;
      const K = readLong;
      auto A = new long[N];
      foreach (i; 0 .. N) {
        A[i] = readLong;
      }
      
      const ans = solve(K, A);
      writeln((A.sum + ans) / 2);
    }
  } catch (EOFException e) {
  }
}