from heapq import *
n,m = map(int, input().split())
grid = [list(input()) for i in range(n)]
visited = [[0 for i in range(m)]for i in range(n)]
depth = [[0 for i in range(m)]for i in range(n)]
ani = []
if grid[0][0]=="F":
ani = ["F","R"]
else: ani = ["R","F"]
a = []
heappush(a,(0,0,0))
while len(a):
node = heappop(a)
depth[node[1]][node[2]] = node[0]
for (i,j) in [(1,0),(-1,0),(0,-1),(0,1)]:
x = node[1] + i
y = node[2] + j
if 0<=x<n and 0<=y<m and grid[x][y] != ".":
if grid[x][y] == ani[node[0]%2] and not visited[x][y]:
visited[x][y] = True
heappush(a, (node[0], x,y))
if grid[x][y] != ani[node[0]%2] and not visited[x][y]:
visited[x][y] = True
heappush(a, (node[0]+1, x,y))
maxi = -1
for i in depth:
maxi = max(maxi, max(i))
print(maxi+1)
