main

#include <climits>
#include <iostream>
#include <vector>
using namespace std;

int main(void) {
  int n, x;
  scanf("%d", &n);
  Trie trie(1024);
  int res = INT_MIN;
  for (int i = 0; i < n; ++i) {
    scanf("%d", &x);
    trie.insert(x);
    res = max(res, static_cast<int>(trie.searchMax(x)));
  }
  printf("%d\n", res);
  return 0;
}

Trie

class Trie {
  class TrieNode {
   public:
    explicit TrieNode() {
      children[0] = 0;
      children[1] = 0;
    }
    inline int &operator[](const int bit) { return children[bit]; }
    inline int operator[](const int bit) const { return children[bit]; }

   private:
    int children[2];
  };

 public:
  explicit Trie(int capacity = 64) {
    nodeVec.reserve(capacity);
    nodeVec.emplace_back();
  }
  void insert(uint32_t x) {
    int j = 0;
    for (int i = 31; i >= 0; --i) {
      const int bit = (x >> i) & 1;
      int &child = nodeVec[j][bit];
      if (!child) {
        child = nodeSize();
        nodeVec.emplace_back();
      }
      j = nodeVec[j][bit];
    }
  }
  uint32_t searchMax(uint32_t x) const {
    int j = 0, res = 0;
    for (int i = 31; i >= 0; --i) {
      const int bit1 = (x >> i) & 1;
      const int bit0 = bit1 ^ 1;
      if (nodeVec[j][bit0]) {
        j = nodeVec[j][bit0];
        res |= 1 << i;
      } else {
        j = nodeVec[j][bit1];
      }
    }
    return res;
  }

 private:
  inline int nodeSize() const { return nodeVec.size(); }
  vector<TrieNode> nodeVec;
};