VirtualData has just found two binary set $A_1, A_2, \cdots, A_n$ and  $B_1, B_2, \cdots, B_n$ ($A_i, B_i ∈ \text{{0, 1}}$ for all $1 \leq i \leq n$) from his virtual machine! He would like to perform the operation described below exactly twice, so that $A_i = B_i$ holds for all $1 \leq i \leq n$ after the two operations.

The operation is: Select two integers $l$ and $r$ ($1 \leq l \leq r \leq n$), change $A_i$ to $(1 - A_i)$ for all $l \leq i \leq r$. VirtualData would like to know the number of ways to do so.

We use the following rules to determine whether two ways are different:

• Let Operation $X = (a_1, a_2, a_3, a_4)$, where $1 \leq a_1 \leq a_2 \leq n$, $1 \leq a_3 \leq a_4 \leq n$, be a valid operation pair denoting that VirtualData selects integers $a_1$ and $a_2$ for the first operation and integers $a_3$ and $a_4$ for the second operation.
• Let Operation $Y = (b_1, b_2, b_3, b_4)$, where $1 \leq b_1 \leq b_2 \leq n$, $1 \leq b_3 \leq b_4 \leq n$, be another valid operation pair denoting that VirtualData selects integers $b_1$ and $b_2$ for the first operation and integers $b_3$ and $b_4$ for the second operation.
• Operation $X$ and Operation $Y$ are considered different if there exists an integer $k$ ($1 \leq k \leq 4$) such that .$a_k \neq b_k$.

Input format

• The first line contains an integer n, denoting the length of binary sequence $A$ and $B$.
• The second line contains a binary string of size $n$, denoting the set $A$.
• The third line contains a binary string of size $n$, denoting the set $B$.

Output format

Print an integer in a new line, representing the number of unique ways given operation can be performed.

Constraints

$1 \leq n \leq 10^6$