diff --git a/15_strict.hs b/15_strict.hs
new file mode 100644
index 0000000..821c959
--- /dev/null
+++ b/15_strict.hs
@@ -0,0 +1,18 @@
+{-# LANGUAGE BangPatterns #-}
+import Data.Function (on)
+import Data.Bits ((.&.))
+        
+count :: Int -> (Int, Int) -> (Int, Int) -> (Int, Int) -> Int -> Int -> Int
+count divisor (factorA, factorB) (seedA, seedB) (divA, divB) acc times =
+    if times == 0 then acc else
+    let !nextA = nextMaskBy factorA divA seedA
+        !nextB = nextMaskBy factorB divB seedB
+        !eq = fromEnum $ ((==) `on` (.&. 0xffff)) nextA nextB
+    in count divisor (factorA, factorB) (nextA, nextB) (divA, divB) (acc + eq) (times - 1)
+    where 
+        nextMaskBy f d s = let t = (f * s) `mod` divisor in if (t .&. d) == 0 then t else nextMaskBy f d t
+
+main :: IO ()
+main = do
+    print $ count 2147483647 (16807, 48271) (634, 301) (0, 0) 0 40000000
+    print $ count 2147483647 (16807, 48271) (634, 301) (3, 7) 0 5000000
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