CodeForces 359A Table

Simon has a rectangular table consisting of n rows and m columns. Simon numbered the rows of the 

table from top to bottom starting from one and the columns — from left to right starting from one.

 We'll represent the cell on the x-th row and the y-th column as a pair of numbers (x, y). The table

 corners are cells: (1, 1), (n, 1), (1, m), (n, m).

Simon thinks that some cells in this table are good. Besides, it's known that no good cell is the corner of the table.

Initially, all cells of the table are colorless. Simon wants to color all cells of his table. In one move,

 he can choose any good cell of table (x1, y1), an arbitrary corner of the table (x2, y2) and color all cells of

 the table (p, q), which meet both inequations: min(x1, x2) ≤ p ≤ max(x1, x2), min(y1, y2) ≤ q ≤ max(y1, y2).

Help Simon! Find the minimum number of operations needed to color all cells of the table. Note that you can color one cell multiple times.

Input:

The first line contains exactly two integers n, m (3 ≤ n, m ≤ 50).

Next n lines contain the description of the table cells. Specifically, the i-th 

line contains m space-separated integers ai1, ai2, ..., aim. If aij equals zero, then

 cell (i, j) isn't good. Otherwise aij equals one. It is guaranteed that at least one 

cell is good. It is guaranteed that no good cell is a corner.

Output:

Print a single number — the minimum number of operations Simon needs to carry out his idea.

Example:

Input

3 3
0 0 0
0 1 0
0 0 0

Output

4

Input

4 3
0 0 0
0 0 1
1 0 0
0 0 0

Output

2

Note:

In the first sample, the sequence of operations can be like this:

For the first time you need to choose cell (2, 2) and corner (1, 1).
For the second time you need to choose cell (2, 2) and corner (3, 3).
For the third time you need to choose cell (2, 2) and corner (3, 1).
For the fourth time you need to choose cell (2, 2) and corner (1, 3).

In the second sample the sequence of operations can be like this:

For the first time you need to choose cell (3, 1) and corner (4, 3).
For the second time you need to choose cell (2, 3) and corner (1, 1).

思路：

因为四个角不会成为good 所以good点可以分为两类：

1：在边上的点。（非角）   2：不在边上的点（非角）

而在边上的点只需两次就能涂满全部格，不在边上的需要四次，即答案只有4和2两种情况。

代码：

#include <cstdio>
#include <iostream>

using namespace std;

int n,m;
int key;

int main(){
	scanf("%d %d",&n,&m);
	for(int i=1 ; i<=n ; i++){
		for(int j=1 ; j<=m ; j++){
			int mid;
			scanf("%d",&mid);
			if(mid == 1){
				if(i == 1 || j == 1 || i == n || j == m)key = 1;
			}
		}
	}
	if(key)printf("2");
	else printf("4");
	return 0;
}