Couldn't match type errors in haskell

I literally started learning haskell in the past few hours following this tutorial. I keep getting Couldn't match type error when trying to compile the following code:

module Main where 
main = do
    let ages = []
    putStrLn "Enter child 1"
    input <- getLine
    -- convert the string to int
    let age1 = read input :: Int
    ages ++ [age1]
    putStrLn "Enter child 2 age"
    input <- getLine
    -- convert the string to int
    let age2 = read input :: Int
    ages ++ [age2]
    putStr "Age of your first child: "
    print age1
    putStr "Age of your second child: "
    print age2

Here is the error:

 Couldn't match type `[]' with `IO'                                                                         
    Expected type: IO Int                                                                                      
      Actual type: [Int]                                                                                       
    In a stmt of a 'do' block: ages ++ [age1]   

I have been searching for several hours trying to understand the issue but have no clue. Why does ages ++ [age2] expects a type IO Int ? and how to resolve this issue?