#include<bits/stdc++.h>

using namespace std;

#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define pf push_front
#define LC k<<1
#define RC k<<1|1
#define IO cin.sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define all(x) (x).begin(), (x).end()
#define SZ(x) ((int)(x).size())
#define rep(i, a, n) for (int i = a; i < n; i++)
#define repn(i, a, n) for (int i = a; i <= n; i++)
#define per(i, a, n) for (int i = (n) - 1; i >= a; i--)
#define pern(i, a, n) for (int i = n; i >= a; i--)

typedef long long LL;
typedef long double LD;
typedef unsigned long long ull;
typedef pair<int, int> PII;
typedef pair<int, LL> PIL;
typedef pair<LL, int> PLI;
typedef pair<double, double> PDD;
typedef pair<ull, ull> PUU;
typedef pair<LL, LL> PLL;

const int N = 510;
const int M = 1100000;
const int mod = 1e9+7;
const int inf = (int)1e9;
const LL INF = 1e18;
const double eps = 1e-9;

mt19937_64 Rand((unsigned long long)new char);
#define rand Rand
int n, m;
string s[N + N];
vector<int> g[M];
vector<PII> edge;
int cal(int x, int y) {
	return (x - 1) * m + y;
}
int dep1[M], dep2[M];
void dfs1(int x, int fa) {
	dep1[x] = dep1[fa] + 1;
	for (auto y: g[x]) if (y != fa) dfs1(y, x);
}
void dfs2(int x, int fa) {
	dep2[x] = dep2[fa] + 1;
	for (auto y: g[x]) if (y != fa) dfs2(y, x);
}
int ans;
int main() {
	IO;
	cin >> n >> m;
	repn(i, 1, n + n + 1) cin >> s[i];
	rep(i, 1, n) repn(j, 1, m) {
		int u = cal(i, j), v = cal(i + 1, j);
		if (s[i + i + 1][j + j - 1] == '.') g[u].pb(v), g[v].pb(u);
		else edge.pb(mp(u, v));
	}
	repn(i, 1, n) rep(j, 1, m) {
		int u = cal(i, j), v = cal(i, j + 1);
		if (s[i + i][j + j] == '.') g[u].pb(v), g[v].pb(u);
		else edge.pb(mp(u, v));
	}
	int st = 1, ed = n * m;
	dfs1(st, 0);
	dfs2(ed, 0);
	ans = dep1[ed];
	for (auto p: edge) {
		int u = p.fi, v = p.se;
		if (dep1[u] + dep2[v] != dep2[u] + dep1[v]) ans = max(ans, min(dep1[u] + dep2[v], dep2[u] + dep1[v]));
	}
	cout << ans << "\n";
	return 0;
}