#include <bits/stdc++.h>
#define rep(i,n) for(int64_t i=0;i < (int64_t)(n);i++)
#define invrep(i,n) for(int64_t i=n-1;i >= 0L;i--)

using namespace std;

//////全探索したいときに開けよ////////
vector<vector<int>> fspattern;
vector<int> fspattern_draft;
int fspcnt = 0;

void setfspattern_core(int floor,int number,int degree){
  if(floor==degree){
    fspattern.at(fspcnt) = fspattern_draft;
    fspcnt++;
  }else{
    rep(i,number){
      fspattern_draft.at(floor) = i;
      setfspattern_core(floor+1,number,degree);
    }
  }
}

void setfspattern(int number,int degree){
  int64_t array_num = 1;
  rep(i,degree){
    array_num *= number;
  }
  fspattern = vector<vector<int>>(array_num,vector<int>(degree));
  fspattern_draft = vector<int>(degree);
  setfspattern_core(0,number,degree);
}

//////nCrのmodを求めたいときに開けよ/////////
//int64_t univMod = 1000000007;
//int64_t factnum = 100000
//vector<int64_t> modfact(factnum);
//vector<int64_t> modinvfact(factnum);

/*void setmodfact(){
  for(int i=0;i<factnum;i++){
    if(i == 0){
      modfact.at(i) = 1;
    }else{
      modfact.at(i) = (modfact.at(i-1)*i)%univMod;
    }
  }
}

int64_t calcmodpower(int64_t a,int64_t n){
  int64_t res = 1;
  while(n != 0){
    if(n & 1){
      res = (res * a) % univMod;
    }
    a = (a*a) % univMod;
    n = n >> 1;
  }
  return res;
}

int64_t calcinverse(int64_t n){
	return calcmodpower(n,univMod-2);
}

void setmodinvfact(){
  for(int i=0;i<factnum;i++){
    if(i==0){
      modinvfact.at(i) = 1;
    }else{
      modinvfact.at(i) = calcmodpower(modfact.at(i),univMod-2);
    }
  }
}

int64_t calcmodcomb(int64_t n,int64_t r){
  return (((modfact.at(n)*modinvfact.at(r))%univMod)*modinvfact.at(n-r))%univMod;
}

int64_t calcmodpositive(int64_t n){
  return (n + ((abs(n)+univMod-1)/univMod)*univMod)%univMod;
}
  
    */


/*
int64_t calcGCD(int64_t a,int64_t b){
	int64_t p = a;
	int64_t q = b;
	int64_t c = a%b;
	while(c != 0){
		p = q;
		q = c;
		c = p%q;
	}
	return q;
}
*/

int main(){
  int h,w;
  cin >> h >> w;
  vector<string> s(h);
  rep(i,h){
    cin >> s.at(i);
  }
  vector<vector<int>> tate(h,vector<int>(w)),yoko(h,vector<int>(w));
  rep(i,h){
    int hoge = 0;
    rep(j,w){
      if(s.at(i).at(j) == '#'){
        tate.at(i).at(j) = -1;
        hoge = 0;
      }else{
        hoge++;
        tate.at(i).at(j) = hoge;
      }
    }
    hoge = 0;
    invrep(j,w){
      if(tate.at(i).at(j) == -1){
        hoge = 0;
      }else{
        if(hoge == 0){
          hoge = tate.at(i).at(j);
        }else{
          tate.at(i).at(j) = hoge;
        }
      }
    }
  }
  /*rep(i,h){
    rep(j,w){
      cout << tate.at(i).at(j);
    }
    cout << endl;
  }*/
  
  rep(j,w){
    int hoge = 0;
    rep(i,h){
      if(s.at(i).at(j) == '#'){
        yoko.at(i).at(j) = -1;
        hoge = 0;
      }else{
        hoge++;
        yoko.at(i).at(j) = hoge;
      }
    }
    hoge = 0;
    invrep(i,h){
      if(yoko.at(i).at(j) == -1){
        hoge = 0;
      }else{
        if(hoge == 0){
          hoge = yoko.at(i).at(j);
        }else{
          yoko.at(i).at(j) = hoge;
        }
      }
    }
  }
  /*rep(i,h){
    rep(j,w){
      cout << yoko.at(i).at(j);
    }
    cout << endl;
  }*/
  int maxnum = 0;
  rep(i,h){
    rep(j,w){
      maxnum = max(tate.at(i).at(j)+yoko.at(i).at(j),maxnum);
    }
  }
  cout << maxnum-1 << endl;
      
          
          
        
}

Measured memory_bytes: 35712