diff --git a/Hydro/H1002/H1002.cpp b/Hydro/H1002/H1002.cpp
new file mode 100644
index 00000000..3dd31c84
--- /dev/null
+++ b/Hydro/H1002/H1002.cpp
@@ -0,0 +1,55 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+int n, a[1000005], ans;
+
+struct node {
+    int val;
+    node* next[2];
+
+    ~node() {
+        for (auto i : next) {
+            delete i;
+        }
+    }
+};
+
+void insert(node* root, int x, int b) {
+    if (!x) {
+        root->val++;
+        return;
+    }
+    if (root->next[(x >> b) & 1] == nullptr) root->next[(x >> b) & 1] = new node();
+    insert(root->next[(x >> b) & 1], x - (((x >> b) & 1) << b), b - 1);
+}
+
+int search(node* root, int x) {
+    int res = 0;
+    node* p = root;
+    for (int i = 30; i >= 0; i--) {
+        if (p == nullptr) break;
+        if (p->next[!((x >> i) & 1)] != nullptr) {
+            res += 1 << i;
+            p = p->next[!((x >> i) & 1)];
+        } else {
+            p = p->next[(x >> i) & 1];
+        }
+    }
+    return res;
+}
+
+int main() {
+    node* root = new node();
+    scanf("%d", &n);
+    for (int i = 0; i < n; i++) {
+        scanf("%d", a + i);
+        insert(root, a[i], 30);
+    }
+    for (int i = 0; i < n; i++) {
+        ans = max(ans, search(root, a[i]));
+    }
+    printf("%d\n", ans);
+    delete root;
+    return 0;
+}