You've gotten an n × m sheet of squared paper. Some of its squares are painted. Let's mark the set of all painted squares as A. Set A is connected. Your task is to find the minimum number of squares that we can delete from set A to make it not connected.

A set of painted squares is called connected, if for every two squares a and b from this set there is a sequence of squares from the set, beginning in a and ending in b, such that in this sequence any square, except for the last one, shares a common side with the square that follows next in the sequence. An empty set and a set consisting of exactly one square are connected by definition.

Input

The first input line contains two space-separated integers n and m (1 ≤ n, m ≤ 50) — the sizes of the sheet of paper. 

Each of the next n lines contains m characters — the description of the sheet of paper: the j-th character of the i-th line equals either "#", if the corresponding square is painted (belongs to set A), or equals "." if the corresponding square is not painted (does not belong to set A). It is guaranteed that the set of all painted squares A is connected and isn't empty.

Output

On the first line print the minimum number of squares that need to be deleted to make set A not connected. If it is impossible, print -1. 

Examples

Input

5 4
####
#..#
#..#
#..#
####


Output

2


Input

5 5
#####
#...#
#####
#...#
#####


Output

2

Note

In the first sample you can delete any two squares that do not share a side. After that the set of painted squares is not connected anymore.

The note to the second sample is shown on the figure below. To the left there is a picture of the initial set of squares. To the right there is a set with deleted squares. The deleted squares are marked with crosses. 

<image>
#include <bits/stdc++.h>
#pragma comment(linker, "/STACK:66777216")
#pragma hdrstop
using namespace std;
inline void sIO() {}
inline void iIO() {
  freopen("input.txt", "r", stdin);
  freopen("output.txt", "w", stdout);
}
inline void fIO(string fn) {
  freopen((fn + ".in").c_str(), "r", stdin);
  freopen((fn + ".out").c_str(), "w", stdout);
}
inline void TM() {}
inline void swap(short& a, short& b) { b ^= a ^= b ^= a; }
inline void swap(int& a, int& b) { b ^= a ^= b ^= a; }
inline void swap(char& a, char& b) { b ^= a ^= b ^= a; }
inline void swap(long long& a, long long& b) { b ^= a ^= b ^= a; }
template <class T>
inline T abs(T x) {
  return x < 0 ? -x : x;
}
template <class T>
inline T sqr(T x) {
  return x * x;
}
template <class T>
inline T min(T& a, T& b) {
  return a < b ? a : b;
}
template <class T>
inline T max(T& a, T& b) {
  return a > b ? a : b;
}
template <class T>
inline T gcd(T a, T b) {
  if (a < b) swap(a, b);
  while (b) {
    a %= b;
    swap(a, b);
  }
  return a;
}
template <class T>
inline T lcm(T a, T b) {
  return a / gcd(a, b) * b;
}
template <class T>
inline bool isPrime(T n) {
  if (n < 2) return false;
  T kk = (T)sqrt(n + 0.);
  for (T i = 2; i <= kk; ++i)
    if (!(n % i)) return false;
  return true;
}
template <class T>
inline string toa(T x) {
  stringstream ss;
  ss << x;
  string ret;
  ss >> ret;
  return ret;
}
template <class T>
inline T ppow(T a, long long b) {
  T ret = 1;
  while (b) {
    if (b & 1) ret *= a;
    a *= a;
    b >>= 1;
  }
  return ret;
}
template <class T>
inline T ppow(T a, long long b, long long md) {
  T ret = 1;
  a %= md;
  while (b) {
    if (b & 1) ret = ret * a % md;
    a = a * a % md;
    b >>= 1;
  }
  return ret % md;
}
inline int toi(string s) {
  stringstream ss;
  ss << s;
  int ret;
  ss >> ret;
  return ret;
}
inline long long tol(string s) {
  stringstream ss;
  ss << s;
  long long ret;
  ss >> ret;
  return ret;
}
inline int Random() { return ((rand() << 16) | rand()); }
inline char upperCase(char ch) {
  return (ch >= 'a' && ch <= 'z') ? ch ^ 32 : ch;
}
inline char lowerCase(char ch) {
  return (ch >= 'A' && ch <= 'Z') ? ch ^ 32 : ch;
}
inline string upperCase(string s) {
  int ls = s.length();
  for (int i = 0; i < ls; ++i)
    if (s[i] >= 'a' && s[i] <= 'z') s[i] ^= 32;
  return s;
}
inline string lowerCase(string s) {
  int ls = s.length();
  for (int i = 0; i < ls; ++i)
    if (s[i] >= 'A' && s[i] <= 'Z') s[i] ^= 32;
  return s;
}
inline int dig(char ch) { return ch - 48; }
inline bool isAlpha(char ch) {
  return (ch >= 'A' && ch <= 'Z' || ch >= 'a' && ch <= 'z');
}
inline bool isDigit(char ch) { return (ch >= '0' && ch <= '9'); }
inline bool isLowerCase(char ch) { return (ch >= 'a' && ch <= 'z'); }
inline bool isUpperCase(char ch) { return (ch >= 'A' && ch <= 'Z'); }
int __;
const int INF = 0x3f3f3f3f;
const long long LINF = 0x3f3f3f3f3f3f3f3fLL;
const double EPS = 1e-9;
const int MD = 1000000007;
const int DX[4] = {1, 0, -1, 0};
const int DY[4] = {0, 1, 0, -1};
int n, ans, ch, cur, m, tot, h, t, q[2555][2], x, y, xx, yy;
bool a[55][55], w[55][55];
bool go() {
  for (int i = 0; i < n; ++i)
    for (int j = 0; j < m; ++j)
      if (a[i][j]) {
        q[0][0] = i;
        q[0][1] = j;
        break;
      }
  h = 0;
  t = 0;
  memset(w, 0, sizeof(w));
  while (h <= t) {
    x = q[h][0];
    y = q[h][1];
    w[x][y] = true;
    for (int i = 0; i < 4; ++i) {
      xx = x + DX[i];
      yy = y + DY[i];
      if (xx >= 0 && yy >= 0 && xx < n && yy < m && a[xx][yy] && !w[xx][yy]) {
        q[++t][0] = xx;
        q[t][1] = yy;
        w[xx][yy] = true;
      }
    }
    ++h;
  }
  for (int i = 0; i < n; ++i)
    for (int j = 0; j < m; ++j)
      if (a[i][j] && !w[i][j]) return true;
  return false;
}
int main() {
  sIO();
  scanf("%d%d\n", &n, &m);
  tot = 0;
  memset(a, 0, sizeof(a));
  for (int i = 0; i < n; ++i) {
    for (int j = 0; j < m; ++j) {
      ch = getchar();
      a[i][j] = ch == '#';
      tot += a[i][j];
    }
    scanf("\n");
  }
  if (tot < 3) {
    printf("-1");
    return 0;
  }
  for (int i = 0; i < n; ++i)
    for (int j = 0; j < n; ++j)
      if (a[i][j]) {
        a[i][j] = false;
        if (go()) {
          printf("1");
          return 0;
        }
        a[i][j] = true;
      }
  ans = INF;
  for (int i = 0; i < n; ++i)
    for (int j = 0; j < m; ++j)
      if (a[i][j]) {
        cur = 0;
        if (i && a[i - 1][j]) ++cur;
        if (j && a[i][j - 1]) ++cur;
        if (i < n - 1 && a[i + 1][j]) ++cur;
        if (j < m - 1 && a[i][j + 1]) ++cur;
        ans = min(ans, cur);
      }
  printf("%d", ans);
  return 0;
}
