Math problem - In a game of "Double Dragon", a flip is worth 4 points and a flop is worth 7 points. Flips and flops are the only way to score. Notice that scores such as 4, 11 (or 4 + 7) and 18 (or 7(2) + 4) are possible to obtain, but scores of 2 and 6 are not possible. What is the largest integer score that is not possible to obtain when playing this game?