Hi Haskellers,

I encounter an strange behavior of haskell program recently.  The following is my program

```haskell
main = do
    _ <- getLine
    arr1 <- getLine
    _ <- getLine
   arr2 <- getLine
   let a = map (read :: String -> Int) (words arr1)
        b = map (read :: String -> Int) (words arr2)

  putStrLn $ show $ (foldl (*) 1 a)
  putStrLn $ show $ a == [1,2,4,8,32,64,128,256,512,1024,2048,4906,8192]
  putStrLn $ show $ (foldl (*) 1 [1,2,4,8,32,64,128,256,512,1024,2048,4906,8192])
```

With the input test file as following:

```test.in
13
1 2 4 8 32 64 128 256 512 1024 2048 4906 8192
9
1 3 9 27 81 243 729 2187 6561
```

The output is as:
```output
0
True
185343439719667835347140608
```

In fact, from the program, we know that a is equal to list  [1,2,4,8,32,64,128,256,512,1024,2048,4906,8192] ,
but the product of a and the literal list is different.

Can anyone tell me why?

Thanks