diff --git a/content/data-structures/MOsAlgorithm.cpp b/content/data-structures/MOsAlgorithm.cpp
new file mode 100644
index 0000000..0e997eb
--- /dev/null
+++ b/content/data-structures/MOsAlgorithm.cpp
@@ -0,0 +1,61 @@
+#define fastio()                                                               \
+  ios::sync_with_stdio(0);                                                     \
+  cin.tie(0);
+
+struct Query {
+  int l, r, idx;
+  bool
+  operator<(const Query &other) const { // first if they are not starting at the
+                                        // same block then sort with l
+                                        // if they are the same then sort buy r
+    int block_size = 450;
+    int block_a = l / block_size;
+    int block_b = other.l / block_size;
+    if (block_a != block_b)
+      return block_a < block_b;
+    return r < other.r;
+  }
+};
+void solve() {
+  fastio();
+  int n, q;
+  cin >> n >> q;
+  vector<int> a(n);
+  for (auto &x : a)
+    cin >> x;
+
+  vector<Query> queries(q); // store queres to make offline process
+  for (int i = 0; i < q; ++i) {
+    int l, r;
+    cin >> l >> r;
+    queries[i] = {--l, --r, i}; // convert to 0-based
+  }
+
+  sort(queries.begin(), queries.end()); // sort to make the largest amount of
+                                        // overlaping with logic at struct
+
+  vector<int> freq(1e6 + 5, 0); // store frq numbers
+  int distinct = 0;
+  int l = 0, r = -1;
+  vector<int> ans(q);
+
+  for (auto query :
+       queries) { // shrink and extend logic and calc the new distinct elements
+    while (r < query.r)
+      if (++freq[a[++r]] == 1)
+        ++distinct;
+    while (r > query.r)
+      if (--freq[a[r--]] == 0)
+        --distinct;
+    while (l < query.l)
+      if (--freq[a[l++]] == 0)
+        --distinct;
+    while (l > query.l)
+      if (++freq[a[--l]] == 1)
+        ++distinct;
+    ans[query.idx] = distinct;
+  }
+
+  for (int x : ans)
+    cout << x << '\n';
+}
diff --git a/content/data-structures/chapter.tex b/content/data-structures/chapter.tex
index 7b60817..b4f86c3 100644
--- a/content/data-structures/chapter.tex
+++ b/content/data-structures/chapter.tex
@@ -17,3 +17,4 @@ \chapter{Data structures}
 \kactlimport{Treap.h}
 \kactlimport{RMQ.h}
 \kactlimport{MoQueries.h}
+\kactlimport{MOsAlgorithm.cpp}