#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < n; i++)
#define repr(i, n) for (int i = n; i >= 0; i--)
typedef long long ll;
int L[2000][2000];
int R[2000][2000];
int U[2000][2000];
int D[2000][2000];
int h,w;

int main() {
  cin >> h >> w;
  vector<string> MAP(h);
  rep(i,h) cin >> MAP[i];

  rep(i,h) {
    rep(j,w) {
      if (MAP[i][j] == '#') continue;
      if (j==0) L[i][j] = 1;
      else L[i][j] = L[i][j-1] + 1;
      if (i==0) U[i][j] = 1;
      else U[i][j] = U[i-1][j] + 1;
    }
  }
  repr(i,h-1) {
    repr(j,w-1) {
      if (MAP[i][j] == '#') continue;
      if (j==w-1) R[i][j] = 1;
      else R[i][j] = R[i][j+1] + 1;
      if (i==h-1) D[i][j] = 1;
      else D[i][j] = D[i+1][j] + 1;
    }
  }
  int ans = 0;
  rep(i,h) rep(j,w) {
    ans = max(ans, L[i][j] + R[i][j] + U[i][j] + D[i][j] - 3);
  }
  cout << ans;
}
