Haskell Program to multiply two numbers

Program

main = do
 let a = 3
 let b = 6
 putStrLn "Product of two numbers"
 print (a * b)

Output

$ ghc multiply_two_numbers.hs 
[1 of 1] Compiling Main             ( multiply_two_numbers.hs, multiply_two_numbers.o )
Linking multiply_two_numbers ...
$ ./multiply_two_numbers 
Product of two numbers
18