#include<bits/stdc++.h>
using namespace std;
const int N = 2011;
int s[N][N], R[N][N], L[N][N], U[N][N], D[N][N];
int main()
{
    int h, w; cin >> h >> w;
    for (int i = 1; i <= h; i++)
    {
        for (int j = 1; j <= w; j++)
        {
            char c; cin >> c;
            s[i][j] = (c == '#');
        }
    }
    for (int i = 1; i <= h; i++)
    {
        for (int j = 1; j <= w; j++)
        {
            if (s[i][j] == 1) continue;
            R[i][j] = R[i][j-1] + 1;
            D[i][j] = D[i-1][j] + 1;
        }
    }
    for (int i = h; i >= 1; i--)
    {
        for (int j = w; j >= 1; j--)
        {
            if (s[i][j] == 1) continue;
            L[i][j] = L[i][j+1] + 1;
            U[i][j] = U[i+1][j] + 1;
        }
    }
    int ans = 0;
    for (int i = 1; i <= h; i++)
    {
        for (int j = 1; j <= w; j++)
        {
            int t = L[i][j] + R[i][j] + U[i][j] + D[i][j] - 3;
            ans = max(ans, t);
        }
    }
    cout << ans;
    return 0;
}