### BUGGY CODE ###

import sys

input = sys.stdin.readline


def main():
    H, W = map(int, input().split())
    S = [None] * (H + 2)
    S[0] = S[-1] = "#" * (W + 2)
    for i in range(1, H + 1):
        S[i] = "".join(["#", input().rstrip(), "#"])

    U = [[-1] * (W + 2) for _ in range(H + 2)]
    D = [[-1] * (W + 2) for _ in range(H + 2)]
    L = [[-1] * (W + 2) for _ in range(H + 2)]
    R = [[-1] * (W + 2) for _ in range(H + 2)]
    for h in range(1, H + 1):
        for w in range(1, W + 1):
            if S[h][w] == "#":
                continue
            if U[h][w] == -1:
                U[h][w] = 0
                d = 0
                while True:
                    d += 1
                    if S[h + d][w] == "#":
                        break
                    U[h + d][w] = d
            if L[h][w] == -1:
                L[h][w] = 0
                d = 0
                while True:
                    d += 1
                    if S[h][w + d] == "#":
                        break
                    L[h][w + d] = d

    for h in reversed(range(1, H + 1)):
        for w in reversed(range(1, W + 1)):
            if S[h][w] == "#":
                continue
            if D[h][w] == -1:
                D[h][w] = 0
                d = 0
                while True:
                    d += 1
                    if S[h - d][w] == "#":
                        break
                    D[h - d][w] = d
            if R[h][w] == -1:
                R[h][w] = 0
                d = 0
                while True:
                    d += 1
                    if S[h][w - d] == "#":
                        break
                    R[h][w - d] = d

    ans = 0
    for h in range(1, H + 1):
        for w in range(1, W + 1):
            dist = U[h][w] + D[h][w] + L[h][w] + R[h][w] + 1
            if ans < dist:
                ans = dist

    print(ans)


if __name__ == "__main__":
    main()


### FIXED CODE ###

H, W = map(int, input().split())
S = [None] * H
for i in range(H):
    S[i] = input()

up = [[0 for w in range(W)] for h in range(H)]
down = [[0 for w in range(W)] for h in range(H)]
left = [[0 for w in range(W)] for h in range(H)]
right = [[0 for w in range(W)] for h in range(H)]

# up and left
for h in range(H):
    for w in range(W):
        if S[h][w] == "#":
            up[h][w] = 0
            left[h][w] = 0
        else:
            # up
            if h == 0:
                up[h][w] = 1
            else:
                up[h][w] = up[h - 1][w] + 1
            # left
            if w == 0:
                left[h][w] = 1
            else:
                left[h][w] = left[h][w - 1] + 1

# down and right
for h in reversed(range(H)):
    for w in reversed(range(W)):
        if S[h][w] == "#":
            down[h][w] = 0
            right[h][w] = 0
        else:
            # down
            if h == H - 1:
                down[h][w] = 1
            else:
                down[h][w] = down[h + 1][w] + 1
            # right
            if w == W - 1:
                right[h][w] = 1
            else:
                right[h][w] = right[h][w + 1] + 1


ans = 0
for h in range(H):
    for w in range(W):
        masu = -3
        masu += up[h][w]
        masu += down[h][w]
        masu += left[h][w]
        masu += right[h][w]
        if masu > ans:
            ans = masu

print(ans)