#include<iostream>
#include<string>
using namespace std;

int main(){
int h,w,i,j,ans=0;
cin>>h>>w;
string s[h];
for(i=0;i<h;i++)cin>>s[i];
int l[h][w],r[h][w],t[h][w],b[h][w];
for(i=0;i<h;i++)
{
for(j=0;j<w;j++)
{
if(s[i][j]=='#'){l[i][j]=0;t[i][j]=0;}
else {l[i][j]=1;t[i][j]=1;if(j-1>=0)l[i][j]+=l[i][j-1];if(i-1>=0)t[i][j]+=t[i-1][j];}
}
}

for(i=h-1;i>=0;i--)
{
for(j=w-1;j>=0;j--)
{
if(s[i][j]=='#'){r[i][j]=0;b[i][j]=0;}
else{r[i][j]=1;b[i][j]=1;if(j+1<w)r[i][j]+=r[i][j+1];if(i+1<h)b[i][j]+=b[i+1][j];}
}
}

for(i=0;i<h;i++)
for(j=0;j<w;j++)
{
if(s[i][j]=='.')
{
ans=max(ans,l[i][j]+r[i][j]+t[i][j]+b[i][j]-3);
}
}
cout<<ans;
}