Taco Chocolate Path

You are given a chocolate bar represented as an n × m grid. Each cell of the grid is either a sweet piece denoted by 'S' or a bitter piece denoted by 'B'.

Your task is to determine whether there exists a path from the top-left corner to the bottom-right corner of the grid that passes only through sweet pieces ('S'). Movement is allowed in the four cardinal directions: up, down, left, and right.

Formally, let \(G\) be an \(n \times m\) grid. You need to check if there exists a sequence of cells \((i_1,j_1), (i_2,j_2), \dots, (i_k,j_k)\) such that:

• \((i_1, j_1) = (0,0)\) and \((i_k, j_k) = (n-1, m-1)\),
• For each \(1 \leq t \leq k\), \(G[i_t][j_t] = 'S'\),
• For each consecutive pair \((i_t, j_t)\) and \((i_{t+1}, j_{t+1})\), the Manhattan distance is 1.

If such a path exists, output YES; otherwise, output NO.

inputFormat

The input is read from standard input (stdin) and is in the following format:

n m
row_1
row_2
... 
row_n

where:

• n is the number of rows.
• m is the number of columns.
• Each row_i is a string of length m consisting only of characters 'S' and 'B'.

outputFormat

Output a single line to standard output (stdout) containing either YES if there exists a valid path, or NO otherwise.

## sample

3 3
SSS
SBS
SSS

YES