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').