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

void main()
{
  auto n = readln.chomp.to!size_t;
  auto ai = readln.split.map!(to!size_t).array;
  writeln(calc(ai));
}

size_t calc(size_t[] ai)
{
  if (ai.length == 1) {
    return 0;
  } else {
    auto maxA = ai.reduce!(max);
    if (maxA == 0) return 0;
    auto b = maxA.bsr;
    auto si = ai.filter!(a => bt(&a, b)).map!(a => a ^ (1 << b)).array;
    auto ri = ai.filter!(a => !bt(&a, b)).array;
    if (si.length == 0) {
      return calc(ri);
    } else if (ri.length == 0) {
      return calc(si);
    } else {
      return min(calc(si), calc(ri)) | (1 << b);
    }
  }
}