Numbers on a Tree

A perfect binary tree has a single root at the top, and every node except the leaves in the lowest layer has exactly two children. A tree of height $H$ has $H+1$ layers: the root sits at depth $0$ and the leaves at depth $H$.

The nodes are labeled by the following rule. The bottom right leaf gets label $1$, and within the same layer the labels increase by $1$ as you move from right to left. Once a layer is finished, move up to the rightmost node of the layer above and label that layer from right to left as well. Repeat until the root is labeled.

A node of the tree can be described by a path that starts at the root and goes down. At a node that is not a leaf you can go to the left child (L) or to the right child (R).

Figure: a labeled tree of height $3$. Path LR leads to the node labeled $11$, and path RRL leads to the node labeled $2$. The root is labeled $15$.

Given the height $H$ of the tree and a path starting at the root, compute the label of the node that the path reaches.

The first line contains the height $H$ of the tree and one string, separated by a space ($1 \le H \le 30$). The string consists only of the letters L and R and describes a path starting at the root. L means going to the left child, and R means going to the right child. The path can be empty, and its length is at most $H$. If the path is empty, the first line contains only $H$.

Print the label of the node that the path reaches on one line.