You have been given a N x M matrix containing lowercase English alphabets ('a' - 'z'). Consider path in which you can either move one unit right of current cell or move unit down of current cell i.e from $(x,\;y)$ you can either move to $(x+1,\;y)$ or move to $(x,\;y+1)$.
Consider all the paths going from $(1,\;1)$ to $(N,\;M)$ in this matrix. Each such path can be described by sequence of labels ('a' - 'z') of all the cells visited on the way. There will be many such paths going from $(1,\;1)$ to $(N,\;M)$. You have to find out lexicographic $K^{th}$ path in the matrix.

Lexicographic $K^{th}$ path can be described as:
Take all the possible paths in a vector and sort them. Print the path at $K^{th}$ position in the array.

INPUT:
First line will consist of two integers N and M. Next N lines will consist of M characters. Next line will consist of number K.

OUTPUT:
Output a string consisting of $N+M-1$ letters denoting the lexicographic $K^{th}$ path. If total number of paths in the matrix are less than K, print 1.

CONSTRAINTS:
$1 \le N * M \le 10^6$
$1 \le K \le 10^{18}$
All the characters in the matrix will be lowercase English alphabets ('a'-'z').