time limit per test: 0.25 sec. memory limit per test: 65536 KB

input: standard output: standard

Consider a necklace made of 2N-1 black and white beads, K of which are black. Necklace is called "beautiful" if it is possible to choose two black beads (not necessarily different) in such a way that one of two necklace parts strictly between them contains exactly N beads. For example, if N=4 and K=3, necklace "WBWBWBW" is beautiful, and necklace "BBWWBWW" is not. You need to find minimal K for which every necklace of 2N-1 beads is beatiful.

Input

The first line of input contains odd integer number 2N-1 (5<=2N-1<=2^31-1).

Output

Output minimal K for which every necklace of 2N-1 beads is beatiful.