Lake with lilies

In the forest the lake with lilies started to bloom. On the first day only one lily bloomed, and then every day the number of blooming lilies doubled. On the n-th day the whole lake was covered with blooming lilies. At what day the half of the lake surface was covered with blooming lilies?

Input

The number of days n (1 < n ≤ 200) when the entire surface of the lake was covered with blooming lilies.

Output

Print the day number when half of the lake surface was covered with blooming lilies.

Examples