diff --git a/S2OJ/1866/1866.cpp b/S2OJ/1866/1866.cpp
new file mode 100644
index 00000000..fbc6dcc7
--- /dev/null
+++ b/S2OJ/1866/1866.cpp
@@ -0,0 +1,75 @@
+#include <iostream>
+#include <algorithm>
+#include <cmath>
+#include <functional>
+#include <iterator>
+#include <numeric>
+#include <vector>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 2e5 + 5;
+
+int n, k, m;
+long long c, d;
+std::vector<long long> a;
+
+bool check(long long x) {
+    std::vector<long long> s(n);
+
+    for (int i = 0; i < n; i++) {
+        if (a[i] >= x) {
+            s[0]++;
+
+            continue;
+        }
+
+        if (d == 0) {
+            if (a[i] + c >= x) {
+                s[std::max(0, i - m + 1)]++;
+                if (i + 1 < n) s[i + 1]--;
+            }
+
+            continue;
+        }
+
+        int l = std::max(0, i - m + 1),
+            r = std::max(l, std::min(i + 1, i - static_cast<int>(std::ceil(static_cast<double>(x - a[i] - c) / d)) + 1));
+
+        s[l]++;
+        if (r < n) s[r]--;
+    }
+
+    std::partial_sum(s.begin(), s.end(), s.begin());
+
+    return std::count_if(s.begin(), s.end(), std::bind(std::greater_equal<>(), std::placeholders::_1, k)) > 0;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n >> k >> m >> c >> d;
+
+    std::copy_n(std::istream_iterator<decltype(a)::value_type>(cin), n, std::back_inserter(a));
+
+    long long l = 0, r = 1e18, res = 0;
+
+    while (l <= r) {
+        long long mid = (l + r) >> 1;
+
+        if (check(mid)) {
+            l = mid + 1;
+            res = mid;
+        } else {
+            r = mid - 1;
+        }
+    }
+
+    cout << res << endl;
+
+    return 0;
+}
+