Helicopters are deployed from the air force's 723rd squadron to Danish naval ships. When initiated in 1962, the naval helicopters consisted of a flight of Alouette helicopters of RDAF squadron 722. Primarily for use on the Thetis class in operations in Greenland and Faroe Islands, but also on Absalon class in international operations and Knud Rasmussen class off Greenland as well as participating in exercises. The independent unit was established in 1977 as "Søværnets Flyvetjeneste" operating  and Westland Lynx  helicopters.  On December 6, 2012, the Danish navy officially ordered nine MH-60R Seahawk helicopters, with all to be delivered by 2018, following a competition on the procurement involving the NH90, AgustaWestlands AW159 Wildcat and the AW101 along with Sikorsky's other bid H-92 Superhawk.
Question: How many years after the Danish navy ordered 9 Seahawk helicopters should they be delivered?
Answer: 6; 6