Hello Codeforces, I am stuck in one of the challenges , all i can think of is dp, but i dont know how to implement that and i also think that the given sample test case( not in image) was wrong because possible arrangements for n=3 and p=1 are {1,2,3},{3,2,1},{3,1,2} that is, there are 3 arrangements but sample output was 2 ; link to image : https://drive.google.com/open?id=1y3CARnR4_KUKP6z3iUcMKhePkZWg6IS4