#define _USE_MATH_DEFINES
#define _SILENCE_CXX17_C_HEADER_DEPRECATION_WARNING
#define _SILENCE_ALL_CXX17_DEPRECATION_WARNINGS
#define _CRT_SECURE_NO_WARNINGS
#include <bits/stdc++.h>
#include<iostream>
#include<unordered_set>

using namespace std;

#define dprint(Exp,...) if(Exp){fprintf(stderr, __VA_ARGS__);}
#define printe(...) fprintf(stderr, __VA_ARGS__);
//#define printe(...) void();
#define printE(...) fprintf(stderr, __VA_ARGS__);
//#define printE(...) void();


#define PrtExp(_Exp)  cerr<< #_Exp <<" = "<< (_Exp)
#define PrtExpN(_Exp)  cerr<< #_Exp <<" = "<< (_Exp) <<"\n"

#define SINT(n) scanf("%d",&n)
#define SINT2(n,m) scanf("%d %d",&n,&m)
#define SINT3(n,m,o) scanf("%d %d %d",&n,&m,&o)
#define SINT4(n,m,o,P) scanf("%d %d %d %d",&n,&m,&o,&P)
#define SINT5(n,m,o,P,q) scanf("%d %d %d %d %d",&n,&m,&o,&P,&q)
#define SLL(n) scanf("%lld",&n)
#define SLL2(n,m) scanf("%lld %lld",&n,&m)
#define SLL3(n,m,o) scanf("%lld %lld %lld",&n,&m,&o)
#define SST(s) scanf("%s",s)
#define SCH(c) scanf("%c",&c)

#define GC() getchar()

#define PINT(n) printf("%d",(int)(n))
#define PINT2(n,m) printf("%d %d",(int)(n),(int)(m))
#define PINT3(n,m,l) printf("%d %d %d",(int)(n),(int)(m),(int)(l))
#define PLL(n) printf("%lld",(long long)(n))
#define PST(s) printf("%s",(s))
#define PCH(s) printf("%c",(s))

#define PINTN(n) printf("%d\n",(int)(n))
#define PINT2N(n,m) printf("%d %d\n",(int)(n),(int)(m))
#define PINT3N(n,m,l) printf("%d %d %d\n",(int)(n),(int)(m),(int)(l))
#define PLLN(n) printf("%lld\n",(long long)(n))
#define PSTN(s) printf("%s\n",(s))
#define PCHN(s) printf("%c\n",(s))

#define PSP() printf(" ")
#define PN() printf("\n")

#define PC(c) putchar(c)
#define CSP (' ')
#define SN ("\n")

#define rep(i,a) for(int i=0;i<a;i++)
#define reP(i,a) for(int i=0;i<=a;i++)
#define Rep(i,a) for(int i=a-1;i>=0;i--)
#define ReP(i,a) for(int i=a;i>=0;i--)

#define rEp(i,a) for(i=0;i<a;i++)
#define rEP(i,a) for(i=0;i<=a;i++)
#define REp(i,a) for(i=a-1;i>=0;i--)
#define REP(i,a) for(i=a;i>=0;i--)

#define repft(i,a,b) for(int i=a;i<b;i++)
#define repfT(i,a,b) for(int i=a;i<=b;i++)
#define Repft(i,a,b) for(int i=a-1;i>=b;i--)
#define RepfT(i,a,b) for(int i=a;i>=b;i--)

#define foreach(a,it) for(auto it = a.begin(); it != a.end(); ++it)

#define FILL(a,v) fill(begin(a),end(a), v)
#define FILL0(a) memset(a,0,sizeof(a))
#define FILL1(a) memset(a,-1,sizeof(a))

typedef long long ll;

typedef unsigned long long ull;
typedef pair<int, int> Pi;
typedef pair<ll, ll>   Pll;


const int INF = 1'010'000'000; // 0x3C33'6080
const ll INFLL = 0x1f1f1f1f1f1f1f1fLL;//2,242,545,357,980,376,863

template <class A, class B> inline ostream& operator<<(ostream& st, const pair<A, B>& P) { return st << "(" << P.first << "," << P.second << ")"; };
template <class A, class B> inline pair<A, B> operator+(const pair<A, B>& P, const pair<A, B>& Q) { return pair<A, B>(P.first + Q.first, P.second + Q.second); };
template <class A, class B> inline pair<A, B> operator-(const pair<A, B>& P, const pair<A, B>& Q) { return pair<A, B>(P.first - Q.first, P.second - Q.second); };

#define fs  first
#define sc  second

int bitCount(unsigned int bits) {
	bits = (bits & 0x55555555) + (bits >> 1 & 0x55555555);    //  2bitごとに計算
	bits = (bits & 0x33333333) + (bits >> 2 & 0x33333333);    //  4bitごとに計算
	bits = (bits & 0x0f0f0f0f) + (bits >> 4 & 0x0f0f0f0f);    //  8bitごとに計算
	bits = (bits & 0x00ff00ff) + (bits >> 8 & 0x00ff00ff);    //  16ビットごとに計算   
	return (bits & 0x0000ffff) + (bits >> 16);    //  32ビット分を計算   
}


int a[2048][2048];
int b[2048][2048];
int c[2048][2048];
int d[2048][2048];

int z[2048][2048];


int main() {
	int h, w;
	cin >> h >> w;

	rep(i, h) {
		string s;
		cin >> s;
		rep(j, w) {
			z[i][j] = s[j] != '#';
		}
	}

	rep(i, h) {
		a[i][0] = z[i][0];
		repft(j, 1, w) {
			a[i][j] = a[i][j - 1] + z[i][j];
			if (z[i][j] == 0) a[i][j] = 0;
		}
	}
	rep(i, w) {
		b[0][i] = z[0][i];
		repft(j, 1, h) {
			b[j][i] = b[j - 1][i] + z[j][i];
			if (z[j][i] == 0) b[j][i] = 0;
		}
	}
	FILL0(c);
	FILL0(d);
	rep(i, h) {
		Rep(j, w) {
			c[i][j] = c[i][j + 1] + z[i][j];
			if (z[i][j] == 0) c[i][j] = 0;
		}
	}
	Rep(i, h) {
		rep(j, w) {
			d[i][j] = d[i + 1][j] + z[i][j];
			if (z[i][j] == 0) d[i][j] = 0;
		}
	}
	int ret = 0;
	/*
	rep(i, h) {
		rep(j, w) {
			printf("%2d ", a[i][j]);
		}
		puts("");
	}
	puts("");

	rep(i, h) {
		rep(j, w) {
			printf("%2d ", b[i][j]);
		}
		puts("");
	}
	puts("");

	rep(i, h) {
		rep(j, w) {
			printf("%2d ", c[i][j]);
		}
		puts("");
	}
	puts("");

	rep(i, h) {
		rep(j, w) {
			printf("%2d ", d[i][j]);
		}
		puts("");
	}
	puts("");


	rep(i, h){
		rep(j, w) {
			printf("%2d ", a[i][j] + b[i][j] + c[i][j] + d[i][j] - 3);
		}
		puts("");
	}
	*/
	rep(i, h) {
		rep(j, w) {
			ret = max(ret, a[i][j] + b[i][j] + c[i][j] + d[i][j] - 3);
		}
	}
	cout << ret << endl;







}

Measured memory_bytes: 82176