### BUGGY CODE ###

h,w=map(int,input().split())
lists=[]
for i in range(h):
    s=input()
    lists.append(s)
ylists=[]
for some in lists:
    some=some+"#"
    cnt=0
    add=[]
    for i in range(w+1):
        if some[i]=="#":
            if cnt==0:
                add.append(0)
                cnt=0
            else:
                add.extend([cnt]*cnt)
                add.append(0)
                cnt=0
                
        elif some[i]!="#":
            cnt+=1
    del add[-1]
    ylists.append(add)
lists1=[]
for i in range(w):
    adds=""
    for j in range(h):
        adds+=lists[j][i]
    lists1.append(adds)
    

tlists=[]
for some in lists1:
    some=some+"#"
    cnt=0
    add=[]
    for i in range(h+1):
        if some[i]=="#":
            if cnt==0:
                add.append(0)
                cnt=0
            else:
                add.extend([cnt]*cnt)
                add.append(0)
                cnt=0
                
        elif some[i]!="#":
            cnt+=1
    del add[-1]
    tlists.append(add)


listss=[]
for i in range(h):
    for j in range(w):
        if ylists[i][j]==0 or  tlists[j][i]==0:
            continue
        else:
            listss.append(ylists[i][j]+tlists[j][i]-1)
print(max(listss))

            

### FIXED CODE ###

#lamp
import sys
input=sys.stdin.readline
h,w=map(int,input().split())
lists=[]
for i in range(h):
    b=list(input())
    lists.append(b)
    
right=[[0 for i in range(w)] for j in range(h)]
left=[[0 for i in range(w)] for j in range(h)]
up=[[0 for i in range(w)] for j in range(h)]
down=[[0 for i in range(w)] for j in range(h)]

#rightの累積和
for i in range(h):
    for j in range(w-1,-1,-1):
        if j==w-1:
            if lists[i][j]=="#":
                right[i][j]=0
            else:
                right[i][j]=1
        else:
            if lists[i][j+1]=="#":
                if lists[i][j]=="#":
                    right[i][j]=0
                else:
                    right[i][j]=1
            elif lists[i][j+1]==".":
                if lists[i][j]=="#":
                    right[i][j]=0
                else:
                    right[i][j]=right[i][j+1]+1


#leftの累積和
for i in range(h):
    for j in range(w):
        if j==0:
            if lists[i][j]=="#":
                left[i][j]=0
            else:
                left[i][j]=1
        else:
            if lists[i][j]=="#":
                left[i][j]=0
            else:
                left[i][j]=left[i][j-1]+1


#upの累積和
for i in range(w):
    for j in range(h):
        if j==0:
            if lists[j][i]=="#":
                up[j][i]=0
            else:
                up[j][i]=1
        else:
            if lists[j][i]=="#":
                up[j][i]=0
            else:
                up[j][i]=up[j-1][i]+1

                
#downの累積和
for i in range(w):
    for j in range(h-1,-1,-1):
        if j==h-1:
            if lists[j][i]=="#":
                down[j][i]=0
            else:
                down[j][i]=1
        else:
            if lists[j][i]=="#":
                down[j][i]=0
            else:
                down[j][i]=down[j+1][i]+1
                
maxi=0
for i in range(h):
    for j in range(w):
        maxi=max(maxi,right[i][j]+left[i][j]+up[i][j]+down[i][j]-3)
print(maxi)