#include <bits/stdc++.h>

using namespace std;

#define FOR(i, a, b) for(int i = (a); i < (b); i++)
#define RFOR(i, a, b) for(int i = (a) - 1; i >= (b); i--)
#define SZ(a) int(a.size())
#define ALL(a) a.begin(), a.end()
#define PB push_back
#define MP make_pair
#define F first
#define S second

typedef long long LL;
typedef vector<int> VI;
typedef pair<int, int> PII;
typedef double db;

int main()
{
	ios::sync_with_stdio(0);
	cin.tie(0);
	
	int n, m;
	cin >> n >> m;
	vector<string> v(n);
	FOR (i, 0, n)
		cin >> v[i];
	
	VI mx(m, -1), mn(m, 74);
	FOR (i, 0, n)
	{
		FOR (j, 0, m)
		{
			if (v[i][j] == '*')
			{
				mx[j] = max(mx[j], i);
				mn[j] = min(mn[j], i);
			}
		}
	}
	VI a;
	FOR (i, 0, m)
	{
		if (mx[i] == -1) continue;
		if (a.empty() || a.back() != mx[i] - mn[i])
			a.PB(mx[i] - mn[i]);
	}
	
	FOR (i, 0, SZ(a))
		cerr << a[i] << ' ';
	cerr << '\n';
	if (SZ(a) == 1)
	{
		cout << 1 << '\n';
		return 0;
	}
	if (SZ(a) <= 5)
	{
		cout << 2 << '\n';
		return 0;
	}	
	FOR (t, 0, 2)
	{
		FOR(i, 1, SZ(a))
		{
			int hL = a[i - 1];
			int hR = a[i];
			FOR(j, 0, SZ(a))
			{
				if(j < i)
					hL = min(hL, a[j]);
				else
					hR = min(hR, a[j]);
			}
			if(hL > hR || a[i - 1] > hR)
				continue;
			bool ok = 1;
			int last = -1;
			FOR(j, 0, i)
			{
				if(a[j] == hL)
				{
					ok &= (j - last - 1 <= 2);
					last = j;
				}
			}
			FOR(j, last + 1, i)
				ok &= a[j] == a[i - 1];
			
			last = SZ(a);
			RFOR(j, SZ(a), i)
			{
				if(a[j] == hR)
				{
					ok &= (last - j - 1 <= 2);
					last = j;
				}
			}
			ok &= (last - (i - 1) - 1 <= 2);
			
			
			if(ok)
			{
				cout << "2\n";
				return 0;
			}
		}
		reverse(ALL(a));
	}
	int hR = *min_element(ALL(a));
	int last = SZ(a);
	bool ok = 1;
	RFOR(j, SZ(a), 0)
	{
		if(a[j] == hR)
		{
			ok &= (last - j - 1 <= 2);
			last = j;
		}
	}
	ok &= (last - (0 - 1) - 1 <= 2);
	
	if(ok)
		cout << "2\n";
	else
		cout << "3\n";
	
	return 0;
}