#!/usr/bin/env python3
import sys
import numpy as np

def solve(H: int, W: int, S: "List[str]"):
    L = [[0 for _ in range(W)] for _ in range(H)]
    R = [[0 for _ in range(W)] for _ in range(H)]
    D = [[0 for _ in range(W)] for _ in range(H)]
    U = [[0 for _ in range(W)] for _ in range(H)]
    for i in range(H):
        for j in range(W):
            if S[i][j] != '#':
                if j == 0:
                    L[i][j] = 1
                else:
                    L[i][j] = L[i][j-1] + 1
            jj = W - 1 - j
            if S[i][jj] != '#':
                if jj == W-1:
                    R[i][jj] = 1
                else:
                    R[i][jj] = R[i][jj+1] + 1
            if S[i][j] != '#':
                if i == 0:
                    D[i][j] = 1
                else:
                    D[i][j] = D[i-1][j] + 1
            ii = H - 1 - i
            if S[ii][j] != '#':
                if ii == H-1:
                    U[ii][j] = 1
                else:
                    U[ii][j] = U[ii+1][j] + 1
    mx = 0 
    for i in range(H):
        for j in range(W):
            m = L[i][j] + R[i][j] + U[i][j] + D[i][j] - 3
            if mx < m:
                mx = m
    print(int(mx))

# Generated by 1.1.4 https://github.com/kyuridenamida/atcoder-tools  (tips: You use the default template now. You can remove this line by using your custom template)
def main():
    def iterate_tokens():
        for line in sys.stdin:
            for word in line.split():
                yield word
    tokens = iterate_tokens()
    H = int(next(tokens))  # type: int
    W = int(next(tokens))  # type: int
    S = [ next(tokens) for _ in range(H) ]  # type: "List[str]"
    solve(H, W, S)

if __name__ == '__main__':
    main()


### FIXED CODE ###

#!/usr/bin/env python3
import sys


def solve(H: int, W: int, S: "List[str]"):
    L = [[0 for _ in range(W)] for _ in range(H)]
    R = [[0 for _ in range(W)] for _ in range(H)]
    D = [[0 for _ in range(W)] for _ in range(H)]
    U = [[0 for _ in range(W)] for _ in range(H)]
    for i in range(H):
        for j in range(W):
            if S[i][j] != '#':
                if j == 0:
                    L[i][j] = 1
                else:
                    L[i][j] = L[i][j-1] + 1
            jj = W - 1 - j
            if S[i][jj] != '#':
                if jj == W-1:
                    R[i][jj] = 1
                else:
                    R[i][jj] = R[i][jj+1] + 1
            if S[i][j] != '#':
                if i == 0:
                    D[i][j] = 1
                else:
                    D[i][j] = D[i-1][j] + 1
            ii = H - 1 - i
            if S[ii][j] != '#':
                if ii == H-1:
                    U[ii][j] = 1
                else:
                    U[ii][j] = U[ii+1][j] + 1
    mx = 0 
    for i in range(H):
        for j in range(W):
            m = L[i][j] + R[i][j] + U[i][j] + D[i][j] - 3
            if mx < m:
                mx = m
    print(int(mx))

# Generated by 1.1.4 https://github.com/kyuridenamida/atcoder-tools  (tips: You use the default template now. You can remove this line by using your custom template)
def main():
    def iterate_tokens():
        for line in sys.stdin:
            for word in line.split():
                yield word
    tokens = iterate_tokens()
    H = int(next(tokens))  # type: int
    W = int(next(tokens))  # type: int
    S = [ next(tokens) for _ in range(H) ]  # type: "List[str]"
    solve(H, W, S)

if __name__ == '__main__':
    main()