Given a natural number
N, a real number
A. Calculate
\(S = {{1 \over A} + {1 \over {A^2}} + {1 \over A^4} +... + {1 \over A^{2\cdot N - 2}} }\)
Input
The first line contains a natural number N (0 < N <= 10). The second line contains a real number А (- 5 <= A<= 5, A!=0).
Imprint
Output the S.
value