#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
typedef long long ll;
using namespace __gnu_pbds;
typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> pbds;
#pragma GCC target ("avx2")
#pragma GCC optimization ("O3")
#pragma GCC optimization ("unroll-loops")
#define ios ios_base::sync_with_stdio(0) ; cin.tie(0) ; cout.tie(0)
#define so sizeof
#define pb push_back
#define cl clear() ;
#define vl vector<ll>
#define sz size()
#define len length()
#define el endl;cout.flush()
#define be begin()
#define fi first
#define se second
#define br break
#define en end()
#define ro return 0
#define br break
#define eb emplace_back
#define con continue
#define ms(x) memset(x , 0, so x)
#define all(x) (x).be , (x).en
#define acc(x) accumulate((x).be , (x).en , 0ll)
#define forn(i,a,b) for(ll i=a;i<=b;++i)
#define rng_58 mt19937 rng(chrono::steady_clock::now().time_since_epoch().count())
#define vll vector<pair<ll,ll> >
#define pll pair<ll,ll>
#define plll pair<ll,pair<ll,ll>>
#define plvl pair<pair<ll,ll> ,ll>
#define mp make_pair
#define trace3(a,b,c) cerr <<"a is " << a << " b is " << b << " c is " << c << el;
#define trace4(a,b,c,d) cerr <<"a is " << a << " b is " << b << " c is " << c <<" d is " << d << el ;
#define trace5(a,b,c,d,e) cerr <<"a is " << a << " b is " << b << " c is " << c <<" d is " << d << " e is " << e << el;
#define trace6(a,b,c,d,e,f) cerr <<"a is " << a << " b is " << b << " c is " << c <<" d is " << d << " e is " << e << " f is " << f << el ;
ll row[2005][2005] , col[2005][2005];
int main()
{
    ios;
    ll h , w ;
    cin >> h >> w;
    char grid[h][w] ;
    ll dots = 0 , obs = 0 ;
    forn(i , 0 , h-1){
       forn(j , 0 , w-1){
          cin >> grid[i][j] ;
          if(grid[i][j] == '.') ++dots ;
          else if(grid[i][j] == '#') ++obs;
       }
    }
    forn(i , 0 , h-1){
       ll cnt = 0 ;
       forn(j , 0 , w-1){
          if(grid[i][j] == '.') ++cnt ;
          else {
            if(grid[i][j] == '#' and cnt > 0){
                row[i][j-1] = cnt ;
                cnt = 0 ;
            }
          }
       }
       if(cnt > 0 ) {
        row[i][w-1] = cnt ;
        cnt = 0 ;
       }
       for(ll j = w-1 ; j>= 0 ; --j){
         if(grid[i][j] == '.' and row[i][j] == 0){
            row[i][j] = row[i][j+1];
         }
       }
    }
    forn(j , 0 , w-1 ){
       ll cnt = 0 ;
       forn(i , 0 , h-1){
          if(grid[i][j] == '.') ++cnt ;
          else {
            if(grid[i][j] == '#' and cnt > 0 ) {
                col[i-1][j] = cnt ;
                cnt = 0 ;
            }
          }
       }
       if(cnt > 0 ){
        col[h-1][j] = cnt ;
        cnt = 0 ;
       }
       for(ll i = h-1 ; i >= 0 ; --i){
         if(grid[i][j] == '.' and col[i][j] == 0 ){
            col[i][j] = col[i+1][j];
         }
       }
    }
    ll maxx = 0LL ;
    forn(i , 0 , h-1){
      forn(j , 0 , w-1){
          if(grid[i][j] == '#') con ;
         ll res = row[i][j] + col[i][j] - 1 ;
         maxx = max(maxx , res) ;
      }
    }
    cout << maxx << el ;
    ro ;
}































Measured memory_bytes: 66944