1006F · Xor-Paths

Problem: There is a rectangular grid of size $n \times m$. Each cell has a number written on it; the number on the cell ($i, j$) is $a_{i, j}$. Your task is to calculate the number of paths from the upper-left cell ($1, 1$) to the bottom-right cell ($n, m$) meeting the following constraints:

• You can move to the right or to the bottom only. Formally, from the cell ($i, j$) you may move to the cell ($i, j + 1$) or to the cell ($i + 1, j$). The target cell can't be outside of the grid.
• The xor of all the numbers on the path from the cell ($1, 1$) to the cell ($n, m$) must be equal to $k$ (xor operation is the bitwise exclusive OR, it is represented as '^' in Java or C++ and "xor" in Pascal).

Find the number of such paths in the given grid.

Input Format: The first line of the input contains three integers $n$, $m$ and $k$ ($1 \le n, m \le 20$, $0 \le k \le 10^{18}$) — the height and the width of the grid, and the number $k$.

The next $n$ lines contain $m$ integers each, the $j$-th element in the $i$-th line is $a_{i, j}$ ($0 \le a_{i, j} \le 10^{18}$).

Output Format: Print one integer — the number of paths from ($1, 1$) to ($n, m$) with xor sum equal to $k$.

Note: All the paths from the first example:

• $(1, 1) \rightarrow (2, 1) \rightarrow (3, 1) \rightarrow (3, 2) \rightarrow (3, 3)$;
• $(1, 1) \rightarrow (2, 1) \rightarrow (2, 2) \rightarrow (2, 3) \rightarrow (3, 3)$;
• $(1, 1) \rightarrow (1, 2) \rightarrow (2, 2) \rightarrow (3, 2) \rightarrow (3, 3)$.

All the paths from the second example:

• $(1, 1) \rightarrow (2, 1) \rightarrow (3, 1) \rightarrow (3, 2) \rightarrow (3, 3) \rightarrow (3, 4)$;
• $(1, 1) \rightarrow (2, 1) \rightarrow (2, 2) \rightarrow (3, 2) \rightarrow (3, 3) \rightarrow (3, 4)$;
• $(1, 1) \rightarrow (2, 1) \rightarrow (2, 2) \rightarrow (2, 3) \rightarrow (2, 4) \rightarrow (3, 4)$;
• $(1, 1) \rightarrow (1, 2) \rightarrow (2, 2) \rightarrow (2, 3) \rightarrow (3, 3) \rightarrow (3, 4)$;
• $(1, 1) \rightarrow (1, 2) \rightarrow (1, 3) \rightarrow (2, 3) \rightarrow (3, 3) \rightarrow (3, 4)$.