Just to clarify the explanation of "exchange the 4 cards" here's a copy/paste from the rules: "Special case: if a player takes a second turn immediately after exchanging the cards (no other player took a turn between the player's turns) and chooses to do this again, he pays 2 weeks for the second exchange action. Of course, he pays no movement cost, as his archeologist is still in Warschau. If he continues to take consecutive turns and continues to choose this action, each subsequent action costs an additional week (e.g.third time is 3 weeks, 4th is 4 weeks, etc.)."
