A sequence consisting of one digit, the number 1 is initially written into a computer. At each successive time step, the computer simultaneously tranforms each digit 0 into the sequence ‘1 0’ and each digit 1 into the sequence ‘0 1’. So, after the first time step, the sequence ‘0 1’ is obtained; after the second, the sequence ‘1 0 0 1’, after the third, the sequence ‘0 1 1 0 1 0 0 1’ and so on. How many pairs of consequitive zeroes will appear in the sequence after n steps? Input Every input line contains one natural number n (0 < n ≤ 1000). Output For each input n print the number of consequitive zeroes pairs that will appear in the sequence after n steps. Sample Input 2 3 Sample Output 1 1