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)); } enum E = 30; void main() { try { for (; ; ) { const N = readInt; const K = readLong; auto A = new int[N]; foreach (i; 0 .. N) { A[i] = readInt; } A.sort; long k = N + 2*K; int ans; foreach_reverse (e; 0 .. E) { long num; for (int i = 0, j = 0; i < N; i = j) { for (; j < N && (A[i] >> e) == (A[j] >> e); ++j) {} const l = (A[i] ^ ans) >> e << e; const r = l + (1 << e); num += 1L * (j - i) * (A.lowerBound(r) - A.lowerBound(l)); } debug writeln(e, " ", ans, " ", num); if (k > num) { k -= num; ans |= 1 << e; } } writeln(ans); } } catch (EOFException e) { } }