Let us consider paths in the plane integer lattice Z × Z consisting only of steps (1,1) and (1,-1) and which never pass below the x-axis. A peak at height k is then defined as a point on the path with coordinate y = k that is immediately preceded by a (1,1) step and immediately followed by a (1,-1) step. The pictures below show two such paths: on the left picture we have 4 peaks (2 peaks at height 2 and 2 peaks at height 3); while on the right picture we have 3 peaks (1 peak at height 1, 1 peak at height 2 and 1 peak at height 3). The problem consists of counting the number of admissible paths starting at (0,0) and ending at (2n, 0) with exactly r peaks at height k. Input The input file contains several test cases, each of them consists of one line with the natural numbers n, r and k which define the problem (first number gives n, second number r, and the last one k). Assume that 1 ≤ n < 20, 0 ≤ r < 20, and 1 ≤ k < 20. Output For each test case, the output is a single integer on a line by itself, answering the problem, being guaranteed to be less than 231. Sample Input 312 10 3 2 Sample Output 2 2002