diff --git a/atcoder/abc071/A/main.cpp b/atcoder/abc071/A/main.cpp
new file mode 100644
index 00000000..4b0ec7aa
--- /dev/null
+++ b/atcoder/abc071/A/main.cpp
@@ -0,0 +1,21 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+using ll = long long;
+
+int main() {
+    ios_base::sync_with_stdio(false);
+    cin.tie(0); cout.tie(0);
+
+    int x, a, b;
+    cin >> x >> a >> b;
+    int da = abs(x - a);
+    int db = abs(x - b);
+    if (da < db) {
+        cout << "A" << endl;
+    } else if (db < da) {
+        cout << "B" << endl;
+    } else throw;
+
+    return 0;
+}
\ No newline at end of file
diff --git a/atcoder/abc071/B/main.cpp b/atcoder/abc071/B/main.cpp
new file mode 100644
index 00000000..82f2cdf5
--- /dev/null
+++ b/atcoder/abc071/B/main.cpp
@@ -0,0 +1,30 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+using ll = long long;
+
+int main() {
+    ios_base::sync_with_stdio(false);
+    cin.tie(0); cout.tie(0);
+
+    string S;
+    cin >> S;
+
+    vector<bool> used(26, false);
+    for (auto ch : S) {
+        int i = (ch - 'a');
+        used[i] = true;
+    }
+    int i;
+    for (i = 0; i < 26; ++i) {
+        if (used[i]) continue;
+        break;
+    }
+    if (i < 26) {
+        cout << char('a' + i) << endl;
+    } else {
+        cout << "None" << endl;
+    }
+
+    return 0;
+}
\ No newline at end of file
diff --git a/atcoder/abc071/C/main.cpp b/atcoder/abc071/C/main.cpp
new file mode 100644
index 00000000..eb643e15
--- /dev/null
+++ b/atcoder/abc071/C/main.cpp
@@ -0,0 +1,43 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+using ll = long long;
+
+int N;
+vector<int> A;
+
+ll solve() {
+    map<int,int> mp;
+    for (auto v : A) {
+        ++mp[v];
+    }
+
+    ll ans = 0;
+    deque<int> Q;
+    for (auto e : mp) {
+        auto v = e.first, c = e.second;
+        if (c <= 1) continue;
+        if (c >= 4) {
+            ans = max(ans, ll(v) * v);
+        }
+        Q.push_back(v);
+        if (Q.size() < 2) continue;
+        if (Q.size() > 2) Q.pop_front();
+        ans = max(ans, ll(Q[0]) * Q[1]);
+    }
+    return ans;
+}
+
+int main() {
+    ios_base::sync_with_stdio(false);
+    cin.tie(0); cout.tie(0);
+
+    cin >> N;
+    A.assign(N, 0);
+    for (int i = 0; i < N; ++i) {
+        cin >> A[i];
+    }
+    cout << solve() << endl;
+
+    return 0;
+}
\ No newline at end of file
diff --git a/atcoder/abc071/D/main.cpp b/atcoder/abc071/D/main.cpp
new file mode 100644
index 00000000..af780370
--- /dev/null
+++ b/atcoder/abc071/D/main.cpp
@@ -0,0 +1,54 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+using ll = long long;
+
+ll MOD = 1000000007;
+
+int N;
+vector<string> S(2);
+
+ll solve() {
+    vector<ll> DP(N, 0);
+    for (int x = 0; x < N; ++x) {
+        if (S[0][x] == S[1][x]) {
+            if (x == 0) {
+                // |
+                DP[x] = 3;
+            } else if (S[0][x-1] == S[1][x-1]) {
+                // ||
+                DP[x] = DP[x-1] * 2 % MOD;
+            } else {
+                // =|
+                DP[x] = DP[x-1];
+            }
+        } else if (x > 0 && S[0][x] == S[0][x-1]) {
+            // =
+            DP[x] = DP[x-1];
+        } else {
+            if (x == 0) {
+                // =
+                DP[x] = 6;
+            } else if (S[0][x-1] == S[1][x-1]) {
+                // |=
+                DP[x] = DP[x-1] * 2 % MOD;
+            } else {
+                // ==
+                DP[x] = DP[x-1] * 3 % MOD;
+            }
+        }
+    }
+    return DP[N-1];
+}
+
+
+int main() {
+    ios_base::sync_with_stdio(false);
+    cin.tie(0); cout.tie(0);
+
+    cin >> N;
+    cin >> S[0] >> S[1];
+    cout << solve() << endl;
+
+    return 0;
+}
\ No newline at end of file