diff --git a/LICENSE b/LICENSE
new file mode 100644
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,22 @@
+Copyright (c) 2018, Metrix.AI
+
+Permission is hereby granted, free of charge, to any person
+obtaining a copy of this software and associated documentation
+files (the "Software"), to deal in the Software without
+restriction, including without limitation the rights to use,
+copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the
+Software is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
+OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+OTHER DEALINGS IN THE SOFTWARE.
diff --git a/Setup.hs b/Setup.hs
new file mode 100644
--- /dev/null
+++ b/Setup.hs
@@ -0,0 +1,2 @@
+import Distribution.Simple
+main = defaultMain
diff --git a/int-multimap.cabal b/int-multimap.cabal
new file mode 100644
--- /dev/null
+++ b/int-multimap.cabal
@@ -0,0 +1,49 @@
+name:
+  int-multimap
+version:
+  0.1.0.1
+synopsis:
+  A data structure that associates each Int key with a set of values
+category:
+  Containers
+homepage:
+  https://github.com/metrix-ai/int-multimap
+bug-reports:
+  https://github.com/metrix-ai/int-multimap/issues
+author:
+  Oleg Shevchenko <shevchenko.cmc@gmail.com>
+maintainer:
+  Metrix.AI Ninjas <ninjas@metrix.ai>
+copyright:
+  (c) 2018, Metrix.AI
+license:
+  MIT
+license-file:
+  LICENSE
+build-type:
+  Simple
+cabal-version:
+  >=1.24
+
+source-repository head
+  type:
+    git
+  location:
+    https://github.com/metrix-ai/int-multimap.git
+
+library
+  hs-source-dirs:
+    library
+  default-extensions:
+    Arrows, BangPatterns, ConstraintKinds, DataKinds, DefaultSignatures, DeriveDataTypeable, DeriveFoldable, DeriveFunctor, DeriveGeneric, DeriveTraversable, EmptyDataDecls, FlexibleContexts, FlexibleInstances, FunctionalDependencies, GADTs, GeneralizedNewtypeDeriving, LambdaCase, LiberalTypeSynonyms, MagicHash, MultiParamTypeClasses, MultiWayIf, NoImplicitPrelude, NoMonomorphismRestriction, OverloadedStrings, PatternGuards, ParallelListComp, QuasiQuotes, RankNTypes, RecordWildCards, ScopedTypeVariables, StandaloneDeriving, TemplateHaskell, TupleSections, TypeFamilies, TypeOperators, UnboxedTuples, StrictData
+  ghc-options: -funbox-strict-fields
+  default-language:
+    Haskell2010
+  exposed-modules:
+    IntMultiMap
+  other-modules:
+  build-depends:
+    base >=4.7 && <5,
+    hashable >=1.2 && <2,
+    containers >=0.5.10 && <0.5.15,
+    unordered-containers >=0.2.8.0 && <0.3
diff --git a/library/IntMultiMap.hs b/library/IntMultiMap.hs
new file mode 100644
--- /dev/null
+++ b/library/IntMultiMap.hs
@@ -0,0 +1,33 @@
+module IntMultiMap
+  where
+
+import qualified Data.IntMap.Strict as A
+import qualified Data.HashSet as B
+import Prelude
+import Data.Int
+import Data.Hashable
+import Data.Foldable
+import Control.Monad
+
+{-|
+
+-}
+newtype IntMultiMap value =
+  IntMultiMap (A.IntMap (B.HashSet value))
+  deriving(Foldable)
+
+delete :: (Hashable value, Eq value) => Int {-^ Key -} -> value -> IntMultiMap value -> IntMultiMap value
+delete key value (IntMultiMap intMap) =
+  IntMultiMap $ A.update f key intMap
+  where
+    f hashSet =
+      mfilter (not . B.null) . Just $ B.delete value hashSet
+
+insert :: (Hashable value, Ord value) => Int -> value -> IntMultiMap value -> IntMultiMap value
+insert key value (IntMultiMap intMap) =
+  IntMultiMap $ A.update (\hash -> Just $ B.insert value hash) key intMap
+
+split :: Int -> IntMultiMap value -> (IntMultiMap value, IntMultiMap value)
+split key (IntMultiMap intMap) = (IntMultiMap oldMap, IntMultiMap newMap)
+  where
+    (oldMap, newMap) = A.split key intMap