Problem Statement
Takahashi is locked within a building.
This building consists of $H×W$ rooms, arranged in $H$ rows and $W$ columns. We will denote the room at the $i$-th row and $j$-th column as $(i,j)$. The state of this room is represented by a character $A_{i,j}$. If $A_{i,j}=$ #, the room is locked and cannot be entered; if $A_{i,j}=$ ., the room is not locked and can be freely entered. Takahashi is currently at the room where $A_{i,j}=$ S, which can also be freely entered.
Each room in the $1$-st row, $1$-st column, $H$-th row or $W$-th column, has an exit. Each of the other rooms $(i,j)$ is connected to four rooms: $(i-1,j)$, $(i+1,j)$, $(i,j-1)$ and $(i,j+1)$.
Takahashi will use his magic to get out of the building. In one cast, he can do the following:
- Move to an adjacent room at most
$K$times, possibly zero. Here, locked rooms cannot be entered. - Then, select and unlock at most
$K$locked rooms, possibly zero. Those rooms will remain unlocked from then on.
His objective is to reach a room with an exit. Find the minimum necessary number of casts to do so.
It is guaranteed that Takahashi is initially at a room without an exit.
Constraints
$3 ≤ H ≤ 800$$3 ≤ W ≤ 800$$1 ≤ K ≤ H×W$- Each
$A_{i,j}$is#,.orS. - There uniquely exists
$(i,j)$such that$A_{i,j}=$S, and it satisfies$2 ≤ i ≤ H-1$and$2 ≤ j ≤ W-1$.
Input
Input is given from Standard Input in the following format:
H W K
A_{1,1}A_{1,2}...A_{1,W}
:
A_{H,1}A_{H,2}...A_{H,W}
Output
Print the minimum necessary number of casts.
样例
3 3 3
#.#
#S.
###
1
3 3 3
###
#S#
###
2
7 7 2
#######
#######
##...##
###S###
##.#.##
###.###
#######
2
题面与样例版权归 AtCoder 及出题人所有;中文翻译由 AI 生成(CI 管线),如有出入请以原文为准。