diff --git a/.DS_Store b/.DS_Store
index 4fcf776..55720eb 100644
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diff --git a/AtCoder/.DS_Store b/AtCoder/.DS_Store
new file mode 100644
index 0000000..d5f2986
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diff --git a/AtCoder/ABC_400/A b/AtCoder/ABC_400/A
new file mode 100755
index 0000000..b63319c
Binary files /dev/null and b/AtCoder/ABC_400/A differ
diff --git a/AtCoder/ABC_400/A.cpp b/AtCoder/ABC_400/A.cpp
new file mode 100644
index 0000000..4ea075a
--- /dev/null
+++ b/AtCoder/ABC_400/A.cpp
@@ -0,0 +1,21 @@
+#include <bits/stdc++.h>
+#define lo long long
+#define INF INT_MAX
+#define LLM LONG_LONG_MAX
+#define endl "\n"
+
+using namespace std;
+/*
+    toothless. #17
+    @fredcss_dev
+*/
+
+int a;
+
+signed main()
+{
+    cin >> a;
+    if (400 % a == 0) cout << 400 / a;
+    else cout << -1;
+    return 0;
+}
\ No newline at end of file
diff --git a/AtCoder/ABC_400/B b/AtCoder/ABC_400/B
new file mode 100755
index 0000000..65c16f7
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diff --git a/AtCoder/ABC_400/B.cpp b/AtCoder/ABC_400/B.cpp
new file mode 100644
index 0000000..214dbaa
--- /dev/null
+++ b/AtCoder/ABC_400/B.cpp
@@ -0,0 +1,55 @@
+#include <bits/stdc++.h>
+#define lo long long
+#define INF INT_MAX
+#define LLM LONG_LONG_MAX
+#define endl "\n"
+
+using namespace std;
+/*
+    toothless. #17
+    @fredcss_dev
+*/
+
+signed main() {
+    int N, M;
+    cin >> N >> M;
+    
+    if (N == 1) {
+        lo total = M + 1LL;
+        if (total > 1e9) {
+            cout << "inf" << endl;
+        } else {
+            cout << total << endl;
+        }
+    } else {
+        lo sum = 0;
+        lo cur = 1;
+        bool f = false;
+        for (int i = 0; i <= M; ++i) {
+            sum += cur;
+            if (sum > 1e9) {
+                f = true;
+                break;
+            }
+            if (i == M) {
+                break;
+            }
+            if (cur > 1e9 / N) {
+                f = true;
+                break;
+            }
+            lo next = cur * N;
+            if (next > (1e9 - sum)) {
+                f = true;
+                break;
+            }
+            cur = next;
+        }
+        if (f) {
+            cout << "inf" << endl;
+        } else {
+            cout << sum << endl;
+        }
+    }
+    return 0;
+}
diff --git a/AtCoder/ABC_400/C b/AtCoder/ABC_400/C
new file mode 100755
index 0000000..f38fa48
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diff --git a/AtCoder/ABC_400/C.cpp b/AtCoder/ABC_400/C.cpp
new file mode 100644
index 0000000..9194b47
--- /dev/null
+++ b/AtCoder/ABC_400/C.cpp
@@ -0,0 +1,41 @@
+#include <bits/stdc++.h>
+#define lo long long
+#define INF INT_MAX
+#define LLM LONG_LONG_MAX
+#define endl "\n"
+
+using namespace std;
+/*
+    toothless. #17
+    @fredcss_dev
+*/
+
+
+signed main() {
+    int N;
+    cin >> N;
+
+    int cnt = 0;
+    int mx = 0;
+    int current = 1;
+
+    while (current <= N) {
+        current *= 2;
+        mx++;
+    }
+    mx--;
+
+    for (int e = 1; e <= mx; ++e) {
+        int m = N / (1 << e);
+        if (m < 1) {
+            continue;
+        }
+        int mx2 = sqrt(m);
+        int cnt = (mx2 + 1) / 2;
+        cnt += cnt;
+    }
+
+    cout << cnt << endl;
+
+    return 0;
+}
\ No newline at end of file
diff --git a/AtCoder/ABC_400/C.py b/AtCoder/ABC_400/C.py
new file mode 100644
index 0000000..e1c30ce
--- /dev/null
+++ b/AtCoder/ABC_400/C.py
@@ -0,0 +1,20 @@
+import math
+
+N = int(input())
+
+count = 0
+e = 1
+
+while True:
+    t = 1 << e
+    if t > N:
+        break
+    Q = N // t
+    if Q == 0:
+        e += 1
+        continue
+    m = math.isqrt(Q)
+    cnt += (m + 1) // 2
+    e += 1
+
+print(cnt)
\ No newline at end of file
diff --git a/AtCoder/ABC_400/D.cpp b/AtCoder/ABC_400/D.cpp
new file mode 100644
index 0000000..6b8c12a
--- /dev/null
+++ b/AtCoder/ABC_400/D.cpp
@@ -0,0 +1,67 @@
+#include <bits/stdc++.h>
+#define lo long long
+#define LLM LONG_LONG_MAX
+#define endl "\n"
+
+using namespace std;
+/*
+    toothless. #17
+    @fredcss_dev
+*/
+
+const lo INF = 1e9;
+const lo dx[] = {1, 0, -1, 0};
+const lo dy[] = {0, 1, 0, -1};
+
+signed main() {
+    lo H, W;
+    cin >> H >> W;
+    vector<string> g(H);
+    for (lo i = 0; i < H; ++i) {
+        cin >> g[i];
+    }
+
+    lo A, B, C, D;
+    cin >> A >> B >> C >> D;
+    --A, --B, --C, --D;
+
+    vector<vector<lo>> dist(H, vector<lo>(W, INF));
+    deque<pair<lo, lo>> q;
+    dist[A][B] = 0;
+    q.epb(A, B);
+
+    while (!q.empty()) {
+        auto [x, y] = q.front();
+        q.pop_front();
+        if (x == C && y == D) {
+            cout << dist[x][y] << '\n';
+            return 0;
+        }
+
+        for (lo i = 0; i < 4; ++i) {
+            lo nx = x + dx[i];
+            lo ny = y + dy[i];
+            if (nx < 0 || nx >= H || ny < 0 || ny >= W) continue;
+            if (g[nx][ny] == '.') {
+                if (dist[nx][ny] > dist[x][y]) {
+                    dist[nx][ny] = dist[x][y];
+                    q.epf(nx, ny);
+                }
+            } else {
+                for (lo j = 1; j <= 2; ++j) {
+                    lo tx = x + j * dx[i];
+                    lo ty = y + j * dy[i];
+                    if (tx < 0 || tx >= H || ty < 0 || ty >= W) break;
+                    if (g[tx][ty] == '.') break;
+                    if (dist[tx][ty] > dist[x][y] + 1) {
+                        dist[tx][ty] = dist[x][y] + 1;
+                        q.epb(tx, ty);
+                    }
+                }
+            }
+        }
+    }
+
+    cout << -1 << '\n';
+    return 0;
+}
\ No newline at end of file
diff --git a/AtCoder/ABC_400/__pycache__/C.cpython-313.pyc b/AtCoder/ABC_400/__pycache__/C.cpython-313.pyc
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index 0000000..15f12d4
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