diff --git a/storage/zeta/cpp/completed/18937.cpp b/storage/zeta/cpp/completed/18937.cpp
new file mode 100644
index 0000000..279dfd1
--- /dev/null
+++ b/storage/zeta/cpp/completed/18937.cpp
@@ -0,0 +1,52 @@
+#include <algorithm>
+#include <cstdint>
+#include <iostream>
+#include <string>
+#define let auto
+#define fn auto
+using namespace std;
+
+typedef size_t usize;
+typedef uint64_t u64;
+
+const let WHITE_KING = "Whiteking";
+const let BLACK_KING = "Blackking";
+
+fn fastio() {
+    ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+}
+
+fn main() -> int {
+    usize n;// count of logs
+    cin >> n;
+
+    let arr = new u64[n];// length of each log
+    for (usize i = 0; i < n; i++) {
+        cin >> arr[i];
+    }
+
+    string who;
+    cin >> who;
+
+    let first = (who[0] == 'W') ? false : true;
+
+    let g = 0;
+    for (usize i = 0; i < n; i++) {
+        let e = arr[i] - 2;
+        g ^= e;
+    }
+    
+    //
+    // W0B WOOOB
+
+    if (g == 0) {
+        cout << (first ? WHITE_KING : BLACK_KING);
+    } else {
+        cout << (!first ? WHITE_KING : BLACK_KING);
+    }
+
+    // free
+    delete[] arr;
+    return 0;
+}
\ No newline at end of file
diff --git a/storage/zeta/cpp/24518.cpp b/storage/zeta/cpp/completed/24518.cpp
similarity index 73%
rename from storage/zeta/cpp/24518.cpp
rename to storage/zeta/cpp/completed/24518.cpp
index f3233bf..c959fcd 100644
--- a/storage/zeta/cpp/24518.cpp
+++ b/storage/zeta/cpp/completed/24518.cpp
@@ -8,7 +8,7 @@
 
 using namespace std;
 
-const usize MOD = 1'000'000'007;
+const usize MOD = 1000000007;
 
 fn fastio() {
     ios::sync_with_stdio(false);
@@ -32,19 +32,19 @@ fn well_known_subarr_sum(usize d, usize lo, usize hi /* exclusive */, usize m) -
     if (lo / m == hi / m) {
         res += ((hi_margin * (hi_margin - 1) / 2) - (lo_margin * (lo_margin - 1) / 2)) * d;
         res %= MOD;
-        return res;
+    } else {
+        res += (hi_margin * (hi_margin - 1) / 2) * d;
+        res %= MOD;
+
+        res += (m * (m - 1) / 2 - lo_margin * (lo_margin - 1) / 2) * d;
+        res %= MOD;
+
+        let d_cycle = (d * (m * (m - 1) / 2) % MOD) % MOD;
+        let cycle_cnt = (hi - lo - (hi_margin + m - lo_margin)) / m;
+        res += cycle_cnt * d_cycle;
+        res %= MOD;
     }
 
-    res += (hi_margin * (hi_margin - 1) / 2) * d;
-    res %= MOD;
-
-    res += (m * (m - 1) / 2 - lo_margin * (lo_margin - 1) / 2) * d;
-    res %= MOD;
-
-    let d_cycle = (d * (m * (m - 1) / 2) % MOD) % MOD;
-    let cycle_cnt = (hi - lo - (hi_margin + m - lo_margin)) / m;
-    res += cycle_cnt * d_cycle;
-    res %= MOD;
     return res;
 }
 
@@ -52,16 +52,16 @@ fn well_known_sum(usize n, usize m) -> usize {
     let res = (usize) 0;
     let steps = vector<usize>();
     steps.push_back(n + 1);
-    for (usize i = 2; i <= (usize) pow(n, 0.5) + 1; i++) {
+    let k = (usize) pow(n, 0.5);
+    for (usize i = 2; i <= k + 1; i++) {
         steps.push_back(n / i + 1);
     }
-
-    for (usize i = 1; i < (usize) pow(n, 0.5); i++) {
+    let step_size = steps.size();
+    for (usize i = 1; i < steps[step_size - 1]; i++) {
         res += (n / i) * (i % m);
         res %= MOD;
     }
 
-    let step_size = steps.size();
     for (usize i = 0; i < step_size - 1; i++) {
         let temp = well_known_subarr_sum(i + 1, steps[i + 1], steps[i], m);
         res += temp;
@@ -84,7 +84,6 @@ fn main() -> int {
     } else if (m == 1) {
         cout << 0 << endl;
     } else {
-        cout << well_known_sum_draft(n, m) << endl;
         cout << well_known_sum(n, m) << endl;
     }
     return 0;