#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace __gnu_pbds;
using namespace std;

typedef tree<int, null_type, less<int>, rb_tree_tag,
        tree_order_statistics_node_update>
        new_data_set;


#define fast ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#define PSET(x,y) fixed<<setprecision(y)<<x
#define pb push_back
#define pf push_front
#define mp make_pair
#define pii pair<int,int>
#define vi vector<int>
#define vip vector<pair<int,int> >
#define ff first
#define ss second
#define int long long
#define SIZE 200010
#define mod 1000000007
#define BIG 998244353
#define s(t) scanf("%d",&t)
#define p(t) printf("%d\n",t)
#define mii map<int,int>
#define MSET(table,i) memset(table, i, sizeof(table))
#define endl '\n'
#define tc int t;cin>>t;while(t--)
#define pi  3.1415926358
#define print(x) for(auto el: x) cout<<el<<" ";cout<<endl
#define bits(x) __builtin_popcount(x)
#define minimum(a,n) min_element(a,a+n)-a
#define maximum(a,n) max_element(a,a+n)-a
#define pqbig priority_queue<int>
#define pqsmall priority_queue<int,vector<int>,greater<int> >
#define all(v) v.begin(),v.end()
#define sitr set<int>:: iterator
#define mitr map<int,int>:: iterator


#define trace1(x)                cerr<<#x<<": "<<x<<endl
#define trace2(x, y)             cerr<<#x<<": "<<x<<" | "<<#y<<": "<<y<<endl
#define trace3(x, y, z)          cerr<<#x<<":" <<x<<" | "<<#y<<": "<<y<<" | "<<#z<<": "<<z<<endl
#define trace4(a, b, c, d)       cerr<<#a<<": "<<a<<" | "<<#b<<": "<<b<<" | "<<#c<<": "<<c<<" | "<<#d<<": "<<d<<endl
#define trace5(a, b, c, d, e)    cerr<<#a<<": "<<a<<" | "<<#b<<": "<<b<<" | "<<#c<<": "<<c<<" | "<<#d<<": "<<d<<" | "<<#e<< ": "<<e<<endl
#define trace6(a, b, c, d, e, f) cerr<<#a<<": "<<a<<" | "<<#b<<": "<<b<<" | "<<#c<<": "<<c<<" | "<<#d<<": "<<d<<" | "<<#e<< ": "<<e<<" | "<<#f<<": "<<f<<endl

const int N=2005;
int leftside[N][N];
int rightside[N][N];
int up[N][N];
int down[N][N];
char arr[N][N];
int n,m;

void fillleft()
{
    for(int i=1;i<=n;i++)
    {
        for(int j=1;j<=m;j++)
        {
            if(arr[i][j]=='.')
                leftside[i][j]=1+leftside[i][j-1];
            else
                leftside[i][j]=0;
        }
    }
}

void fillright()
{
    for(int i=1;i<=n;i++)
    {
        for(int j=m;j>=1;j--)
        {
            if(arr[i][j]=='.')
                rightside[i][j]=1+rightside[i][j+1];
            else
                rightside[i][j]=0;
        }
    }
}
void fillup()
{
    for(int j=1;j<=m;j++)
    {
        for(int i=1;i<=n;i++)
        {
            if(arr[i][j]=='.')
                up[i][j]=1+up[i-1][j];
            else
                up[i][j]=0;
        }
    }
}
void filldown()
{
    for(int j=1;j<=m;j++)
    {
        for(int i=n;i>=1;i--)
        {
            if(arr[i][j]=='.')
                down[i][j]=1+down[i+1][j];
            else
                down[i][j]=0;
        }
    }
}

int32_t main()
{
    fast;
    cin>>n>>m;
    for(int i=1;i<=n;i++)
        for(int j=1;j<=m;j++)
            cin>>arr[i][j];

    fillleft();
    fillright();
    fillup();
    filldown();
    int ans=0;
    for(int i=1;i<=n;i++)
    {
        for(int j=1;j<=m;j++)
        {
            if(arr[i][j]=='#')
                continue;

            int l=leftside[i][j]-1;
            int r=rightside[i][j]-1;
            int u=up[i][j]-1;
            int d=down[i][j]-1;
            int val=l+r+u+d+1;
            ans=max(ans,val);
        }
    }
    cout<<ans;
}

Measured memory_bytes: 129792