import sys
input = sys.stdin.readline

H, W = map(int, input().split())
C = [input().strip() for _ in range(H)]

INF = 10**18
WW = 2 * W - 1

prev2 = [INF] * WW
prev1 = [INF] * WW

for x in range(2 * H - 1):
    cur = [INF] * WW

    for y in range(WW):
        if x % 2 == 0 and y % 2 == 0 and C[x // 2][y // 2] == "#":
            continue

        v = INF

        if x == 0 and y == 0:
            v = 0
        if x:
            v = min(v, prev1[y] + 1)
        if y:
            v = min(v, cur[y - 1] + 1)
        if x >= 2 and x % 2 == 0:
            v = min(v, prev2[y] + 1)
        if y >= 2 and y % 2 == 0:
            v = min(v, cur[y - 2] + 1)

        cur[y] = v

    prev2, prev1 = prev1, cur

ans = prev1[-1]
print(-1 if ans >= INF else ans)