### BUGGY CODE ###

h,w=map(int,input().split())
lists1=[0]*h
import sys
input=sys.stdin.readline
for i in range(h):
    s=list(input())
    lists1[i]=s

  
    
uselists1=[0]*h
judgelist=[]
for j in  range(h):
    some=lists1[j]
    count=0
    addlist=[0]*w
    sublist=[]
    for k in range(w):
        if some[k]=="#" and count==0:
            sublist.append(0)
            
            count=0
        elif some[k]=="#" and count>=1:
          sublist.append(count)
          sublist.append(0)
          count=0
          
        if some[k]==".":
            count+=1
            if k==w-1:
                sublist.append(count)
    judgelist.append(sublist)

reallist1=[[] for _ in range(h)]
for i in range(h):
  use=judgelist[i]
  for j in range(len(use)):
    if use[j]!=0:
    	for k in range(use[j]):
    		reallist1[i].append(use[j])
    else:
      reallist1[i].append(0)


lists2=[0]*w
for i in range(w):
  s=[0]*h
  for j in range(h):
    s[j]=lists1[j][i]
  lists2[i]=s


h,w=w,h
judgelist2=[]
for j in  range(h):
    some=lists2[j]
    count=0
    addlist=[0]*w
    sublist=[]
    for k in range(w):
        if some[k]=="#" and count==0:
            sublist.append(0)
            
            count=0
        elif some[k]=="#" and count>=1:
          sublist.append(count)
          sublist.append(0)
          count=0
          
        if some[k]==".":
            count+=1
            if k==w-1:
                sublist.append(count)
    judgelist2.append(sublist)
   
reallist2=[[] for _ in range(h)]
for i in range(h):
  use=judgelist2[i]
  for j in range(len(use)):
    if use[j]!=0:
    	for k in range(use[j]):
    		reallist2[i].append(use[j])
    else:
      reallist2[i].append(0)
               

answer=0
h,w=w,h
for i in range(h):
  for j in range(w):
    if reallist1[i][j]==0 or reallist2[j][i]==0:
      continue
    else:
      answer=max(answer,reallist1[i][j]+reallist2[j][i]-1)
      
print(answer)


### 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)