diff --git a/AtCoder/arc181_a.cpp b/AtCoder/arc181_a.cpp
new file mode 100644
index 0000000..74ad844
--- /dev/null
+++ b/AtCoder/arc181_a.cpp
@@ -0,0 +1,60 @@
+/**
+ * @file arc181_a.cpp
+ * @author Macesuted (i@macesuted.moe)
+ * @date 2024-08-04
+ *
+ * @copyright Copyright (c) 2024
+ *
+ */
+
+#include <bits/stdc++.h>
+using namespace std;
+
+#ifndef LOCAL
+#define endl '\n'
+#endif
+
+bool mem1;
+
+#define maxn 200005
+
+int a[maxn];
+
+void solve(void) {
+    int n;
+    cin >> n;
+    for (int i = 1; i <= n; i++) cin >> a[i];
+
+    bool chk = true;
+    for (int i = 1; i <= n; i++) chk &= (a[i] == i);
+    if (chk) return cout << 0 << endl, void();
+
+    for (int i = 1, maxv = 0; i <= n; i++) {
+        maxv = max(maxv, a[i - 1]);
+        if (a[i] == i && maxv == i - 1) return cout << 1 << endl, void();
+    }
+
+    if (a[1] != n || a[n] != 1) return cout << 2 << endl, void();
+
+    cout << 3 << endl;
+
+    return;
+}
+
+bool mem2;
+
+int main() {
+    ios::sync_with_stdio(false), cin.tie(nullptr);
+#ifdef LOCAL
+    cerr << "Memory Cost: " << abs(&mem1 - &mem2) / 1024. / 1024. << "MB" << endl;
+#endif
+
+    int _ = 1;
+    cin >> _;
+    while (_--) solve();
+
+#ifdef LOCAL
+    cerr << "Time Cost: " << clock() * 1000. / CLOCKS_PER_SEC << "MS" << endl;
+#endif
+    return 0;
+}
\ No newline at end of file
diff --git a/AtCoder/arc181_b.cpp b/AtCoder/arc181_b.cpp
new file mode 100644
index 0000000..f12bad8
--- /dev/null
+++ b/AtCoder/arc181_b.cpp
@@ -0,0 +1,53 @@
+/**
+ * @file arc181_b.cpp
+ * @author Macesuted (i@macesuted.moe)
+ * @date 2024-08-04
+ *
+ * @copyright Copyright (c) 2024
+ *
+ */
+
+#include <bits/stdc++.h>
+using namespace std;
+
+#ifndef LOCAL
+#define endl '\n'
+#endif
+
+bool mem1;
+
+bool solve(void) {
+    string a, X, Y;
+    cin >> a >> X >> Y;
+    int64_t n = a.size(), cnt[2][2] = {{0, 0}, {0, 0}};
+    for (char c : X) cnt[0][c - '0']++;
+    for (char c : Y) cnt[1][c - '0']++;
+    if ((cnt[0][0] > cnt[1][0] && cnt[0][1] > cnt[1][1]) || (cnt[0][0] < cnt[1][0] && cnt[0][1] < cnt[1][1])) return false;
+    int64_t x = abs(cnt[0][0] - cnt[1][0]), y = abs(cnt[0][1] - cnt[1][1]);
+    if (x == 0) return true;
+    if (y == 0) return false;
+    if (x * n % y) return false;
+    int64_t m = x * n / y;
+    int len = gcd(n, m);
+    for (int i = 0; i + len < n; i++)
+        if (a[i] != a[i + len]) return false;
+    return true;
+}
+
+bool mem2;
+
+int main() {
+    ios::sync_with_stdio(false), cin.tie(nullptr);
+#ifdef LOCAL
+    cerr << "Memory Cost: " << abs(&mem1 - &mem2) / 1024. / 1024. << "MB" << endl;
+#endif
+
+    int _ = 1;
+    cin >> _;
+    while (_--) cout << (solve() ? "Yes" : "No") << endl;
+
+#ifdef LOCAL
+    cerr << "Time Cost: " << clock() * 1000. / CLOCKS_PER_SEC << "MS" << endl;
+#endif
+    return 0;
+}
\ No newline at end of file
diff --git a/AtCoder/arc181_c.cpp b/AtCoder/arc181_c.cpp
new file mode 100644
index 0000000..1067746
--- /dev/null
+++ b/AtCoder/arc181_c.cpp
@@ -0,0 +1,52 @@
+/**
+ * @file arc181_b.cpp
+ * @author Macesuted (i@macesuted.moe)
+ * @date 2024-08-04
+ *
+ * @copyright Copyright (c) 2024
+ *
+ */
+
+#include <bits/stdc++.h>
+using namespace std;
+
+#ifndef LOCAL
+#define endl '\n'
+#endif
+
+bool mem1;
+
+#define maxn 505
+
+int p[maxn], q[maxn], a[maxn][maxn];
+
+void solve(void) {
+    int n;
+    cin >> n;
+    for (int i = 1; i <= n; i++) cin >> p[i];
+    for (int i = 1; i <= n; i++) cin >> q[i];
+    for (int i = 1; i <= n; i++)
+        for (int j = n - i + 1; j <= n; j++) a[p[i]][q[j]] = 1;
+    for (int i = 1; i <= n; i++) {
+        for (int j = 1; j <= n; j++) cout << a[i][j];
+        cout << endl;
+    }
+    return;
+}
+
+bool mem2;
+
+int main() {
+    ios::sync_with_stdio(false), cin.tie(nullptr);
+#ifdef LOCAL
+    cerr << "Memory Cost: " << abs(&mem1 - &mem2) / 1024. / 1024. << "MB" << endl;
+#endif
+
+    int _ = 1;
+    while (_--) solve();
+
+#ifdef LOCAL
+    cerr << "Time Cost: " << clock() * 1000. / CLOCKS_PER_SEC << "MS" << endl;
+#endif
+    return 0;
+}
\ No newline at end of file
diff --git a/AtCoder/arc181_d.cpp b/AtCoder/arc181_d.cpp
new file mode 100644
index 0000000..39c52e6
--- /dev/null
+++ b/AtCoder/arc181_d.cpp
@@ -0,0 +1,69 @@
+/**
+ * @file arc181_b.cpp
+ * @author Macesuted (i@macesuted.moe)
+ * @date 2024-08-04
+ *
+ * @copyright Copyright (c) 2024
+ *
+ */
+
+#include <bits/stdc++.h>
+using namespace std;
+
+#ifndef LOCAL
+#define endl '\n'
+#endif
+
+bool mem1;
+
+#define maxn 200005
+
+class FenwickTree {
+   private:
+    int tree[maxn];
+
+   public:
+    void insert(int p) {
+        for (int i = p; i < maxn; i += i & -i) tree[i]++;
+        return;
+    }
+    int query(int p) {
+        int sum = 0;
+        for (int i = p; i; i -= i & -i) sum += tree[i];
+        return sum;
+    }
+} FT;
+
+int a[maxn], p[maxn], pos[maxn], dt[maxn];
+
+void solve(void) {
+    int n, q;
+    cin >> n;
+    int64_t ans = 0;
+    for (int i = 1; i <= n; i++) cin >> a[i], p[i] = i - 1 - FT.query(a[i]), FT.insert(a[i]), ans += p[i];
+    cin >> q;
+    for (int i = 1; i <= q; i++) cin >> pos[i];
+    for (int i = 1, j = 1; i <= n; i++) {
+        while (j <= q && pos[j] < i) j++;
+        if (j <= q) dt[j]--, dt[min(q + 1, j + p[i])]++;
+    }
+    for (int i = 1; i <= q; i++) cout << (ans += (dt[i] += dt[i - 1])) << endl;
+    return;
+}
+
+bool mem2;
+
+int main() {
+    ios::sync_with_stdio(false), cin.tie(nullptr);
+#ifdef LOCAL
+    cerr << "Memory Cost: " << abs(&mem1 - &mem2) / 1024. / 1024. << "MB" << endl;
+#endif
+
+    int _ = 1;
+    while (_--) solve();
+
+#ifdef LOCAL
+    cerr << "Time Cost: " << clock() * 1000. / CLOCKS_PER_SEC << "MS" << endl;
+#endif
+    return 0;
+}
\ No newline at end of file