[Haskell-cafe] Last statement in 'do' must be an expression error.

Hi. When trying to compilke this code: {...} 8.if (a == 0) && (b == 0) 9. then do 10. nr1 <- read (prompt "enter 1. number: ") 11. nr2 <- read (prompt "enter 2. number: ") 12. else do 13. let nr1 = a 14. nr2 = b {...} The compiler tells me thats there's an error on line 10: "The last statement in a 'do' construct mesy be an expression" Could you tell me how to change it so that the "declaration" of the first nr1 and nr2 is still in the "then" block.