TC SRM 526

p250 is an easy one and the only one that I submitted. However a mistake in
ducks[c]=1 instead of the correct ducks[r] = 1 cost all points. Now back to 1254, close to div2 now.

p500 is a combinatorial game and seems not difficult, however I cannot get the last sample case to pass. The problem is about a game. Two players, A and B, remove pebbles from a pile with n pebbles initially. A moves first. A can remove between 1 to K pebbles from the pile, but the remaining number must be a prime. B can remove between 1 to K pebbles, but the remaining number must be a composite (>=2 and not prime). Now decide the value of the game. If a player wins, it tries to win with minimum steps, if lose, it tries to maximize steps. The natural way is to calc(N,turn) to check whether the current turn wins. However each move needs to check K possible numbers and there are 2N configurations, for a total of 10^6^2 = 10^12, which will certainly TLE. But there has to be something about primes, can you check less configurations or check each configuration faster?