diff --git a/IEEExtreme/18/cheap_construction.cpp b/IEEExtreme/18/cheap_construction.cpp
new file mode 100644
index 00000000..b8bf5c67
--- /dev/null
+++ b/IEEExtreme/18/cheap_construction.cpp
@@ -0,0 +1,61 @@
+// problem statement: https://csacademy.com/ieeextreme-practice/task/cheap-construction
+
+#include <bits/stdc++.h>
+
+using namespace std;
+
+constexpr int P = 233;
+constexpr int MOD1 = 1e9 + 7, MOD2 = 19260817;
+constexpr int MAXN = 5e3 + 10;
+
+string str;
+int n;
+int res[MAXN], val1[MAXN], val2[MAXN], pow1[MAXN], pow2[MAXN];
+unordered_map<long long, vector<int>> pos;
+
+void hash_whole_str() {
+    val1[0] = str[0] - 'a' + 1, val2[0] = str[0] - 'a' + 1;
+    for (int i = 1; i < n; i++) {
+        val1[i] = (1LL * val1[i - 1] * P % MOD1 + str[i] - 'a' + 1) % MOD1;
+        val2[i] = (1LL * val2[i - 1] * P % MOD2 + str[i] - 'a' + 1) % MOD2;
+    }
+    pow1[0] = 1, pow2[0] = 1;
+    for (int i = 1; i <= n; i++) {
+        pow1[i] = 1LL * pow1[i - 1] * P % MOD1;
+        pow2[i] = 1LL * pow2[i - 1] * P % MOD2;
+    }
+}
+
+long long hash_sub_str(int start, int len) {
+    int end = start + len - 1;
+    return (long long)(val1[end] - 1LL * val1[start - 1] * pow1[len] % MOD1 + MOD1) % MOD1 << 32 |
+           (val2[end] - 1LL * val2[start - 1] * pow2[len] % MOD2 + MOD2) % MOD2;
+}
+
+int main() {
+    ios::sync_with_stdio(false);
+    cin >> str;
+    n = str.length();
+    hash_whole_str();
+    for (int len = 1; len <= n; len++) {
+        for (int start = 0; start + len - 1 < n; start++) {
+            pos[hash_sub_str(start, len)].push_back(start);
+        }
+        for (auto &&item : pos) {
+            int cnt = item.second[0];
+            int las = item.second[0] + len - 1;
+            for (int i = 1; i < item.second.size(); i++) {
+                if (las < item.second[i]) {
+                    cnt += item.second[i] - las;
+                }
+                las = item.second[i] + len - 1;
+            }
+            cnt += n - las;
+            if (res[cnt] == 0) { res[cnt] = len; }
+        }
+        pos.clear();
+    }
+    for (int i = 1; i <= n; i++) { cout << res[i] << (i == n ? "\n" : " "); }
+    return 0;
+}
+