How to Declare and Define an Integer Type in F# ?

// AbundantCode F# Tutorials and Code snippets
open System
[<EntryPoint>]
let main argv = 
    let integerVal1 = 10 
    let integerVal2 = 10l
    Console.WriteLine(integerVal1)
    Console.WriteLine(integerVal2)
    let retval = Console.ReadLine()
    0 // return an integer exit code