diff --git a/solved/LeetCode/Challenges/2020/January/10.cc b/solved/LeetCode/Challenges/2020/January/10.cc
new file mode 100644
index 00000000..f6885556
--- /dev/null
+++ b/solved/LeetCode/Challenges/2020/January/10.cc
@@ -0,0 +1,71 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+#include "../../../template.cc"
+
+using int64 = long long int;
+
+// Single modification, range query.
+struct SegTree {
+  int n;
+  vector<int> t;
+
+  SegTree(int N) : n(N), t(2 * N) {}
+
+  void add(int p, int value) {
+    for (t[p += n] += value; p > 1; p >>= 1) {
+      t[p>>1] = t[p] + t[p^1];
+    }
+  }
+
+  // sum on interval [l, r)
+  int query(int l, int r) {
+    int res = 0;
+    for (l += n, r += n; l < r; l >>= 1, r >>= 1) {
+      if (l&1) res += t[l++];
+      if (r&1) res += t[--r];
+    }
+    return res;
+  }
+};
+
+
+class Solution {
+ public:
+  int64 mod = 1e9 + 7;
+    int createSortedArray(vector<int>& instructions) {
+      int mmax = (*max_element(instructions.begin(), instructions.end())) + 10;
+      SegTree tree(mmax + 1);
+      int ans = 0;
+      for (auto val: instructions) {
+        int cur = min(tree.query(0, val), tree.query(val + 1, mmax));
+        ans = (ans + cur) % mod;
+        tree.add(val, 1);
+      }
+      return ans;
+    }
+ private:
+
+};
+
+struct Test {
+  vector<int> instructions;
+  int expected;
+};
+
+int main() {
+  vector<Test> test = {
+    { {1,5,6,2}, 1},
+    { {1,2,3,6,5,4}, 3},
+    { {1,3,3,3,2,4,2,1,2}, 4},
+    { {1,2,1,2,1,2,1,2,1,2,1,2}, 0}
+  };
+  for (auto t : test) {
+    Solution sol;
+    int actual = sol.createSortedArray(t.instructions);
+    debug(t.instructions, t.expected, actual);
+    assert(t.expected == actual);
+  }
+  return 0;
+}
diff --git a/solved/LeetCode/template.cc b/solved/LeetCode/template.cc
new file mode 100644
index 00000000..1f0229a4
--- /dev/null
+++ b/solved/LeetCode/template.cc
@@ -0,0 +1,67 @@
+void print(std::ostream& out) { out << std::endl; }
+
+template <typename T, typename T2>
+void printOne(std::ostream& out, const std::pair<T, T2>& a) {
+  out << "{" << a.first << ", " << a.second << "}";
+}
+
+template <typename T>
+void printOne(std::ostream& out, const T& a) {
+  out << a;
+}
+
+template <typename T>
+void printOne(std::ostream& out, const std::vector<T>& a) {
+  out << "{";
+  for (int i = 0; i < a.size(); i++) {
+    if (i) out << ", ";
+    printOne(out, a[i]);
+  }
+  out << "}";
+}
+
+template <typename T>
+void printOne(std::ostream& out, const std::deque<T>& a) {
+  out << "{";
+  for (int i = 0; i < a.size(); i++) {
+    if (i) out << ", ";
+    printOne(out, a[i]);
+  }
+  out << "}";
+}
+
+template <typename T>
+void printOne(std::ostream& out, const std::set<T>& a) {
+  out << "{";
+  for (auto it : a) {
+    printOne(out, it);
+    out << ",";
+  }
+  out << "}";
+}
+
+template <typename T, typename  V>
+void printOne(std::ostream& out, const std::map<T, V>& a) {
+  out << "{";
+  for (auto [key, val] : a) {
+    out << "["; printOne(out, key); out << " = "; printOne(out, val); out << "],";
+  }
+  out << "}";
+}
+
+
+template <typename T, typename... Tail>
+void print(std::ostream& out, const T& first, const Tail... tail) {
+  printOne(out, first);
+  if (sizeof...(tail) != 0) {
+    out << ", ";
+  }
+  print(out, tail...);
+}
+
+#ifdef LOCAL_CP
+#define debug(...) \
+    std::cerr << "[DEBUG] [" << #__VA_ARGS__ << "] = ", print(std::cerr, __VA_ARGS__)
+#else
+#define debug(...) 0
+#endif