Which gospel were they preaching?

Luke 9:6 And they departed, and went through the towns, preaching the gospel, and healing every where.

They couldn't have been preaching the following, could they?

I Corinthians 15:1 Moreover, brethren, I declare unto you the gospel which I preached unto you, which also ye have received, and wherein ye stand;

  2 By which also ye are saved, if ye keep in memory what I preached unto you, unless ye have believed in vain.

  3 For I delivered unto you first of all that which I also received, how that Christ died for our sins according to the scriptures;

  4 And that he was buried, and that he rose again the third day according to the scriptures:

Because, Luke 9: 6 was well before the crucifixion and resurrection.

And even when Jesus foretold his disciples about the resurrection, they didn't understand until after it happened.