#define _CRT_SECURE_NO_WARNINGS
#define _USE_MATH_DEFINES

#include <bits/stdc++.h>
using namespace std;
using i32 = int32_t;  using i64 = int64_t;  using str = string;
using u32 = uint32_t; using u64 = uint64_t; using usize = size_t;
using f64 = double_t; template <typename T> using vec = vector<T>;
#define times(n, i) for (i64 i = 0; i < (n); ++i)
#define range(n, m, i) for (i64 i = (n); i < (m); ++i)
#define upto(n, m, i) for (i64 i = (n); i <= (m); ++i)
#define downto(n, m, i) for (i64 i = (n); i >= (m); --i)
#define foreach(xs, x) for (auto &x : (xs))
#define all(xs) (xs).begin(), (xs).end()
#define sortall(xs) sort(all(xs))
#define reverseall(xs) reverse(all(xs))
#define uniqueall(xs) (xs).erase(unique(all(xs)), (xs).end())
#define maximum(xs) (*max_element(all(xs)))
#define minimum(xs) (*min_element(all(xs)))
#define even(x) (((x) & 1) == 0)
#define odd(x) (((x) & 1) == 1)
#define append emplace_back
const i64 MOD = 1000000007;

i32 h, w;
vec<str> m;
i32 v[2][3002][3002];
i32 ox[8] = { -1, -1, 0, 1, 1, 1, 0, -1 };
i32 oy[8] = { 0, -1, -1, -1, 0, 1, 1, 1 };

i32 main()
{
    cin >> h >> w;
    m.resize(h+2);
    times(w+2, x) {
        m[0] += '.';
        m[h+1] += '.';
    }
    times(h, i) {
        str s; cin >> s;
        m[i+1] = '.' + s + '.';
    }
    h += 2; w += 2;

    i32 ans = 0;
    i32 b = 0;
    times(max(h, w)/2 + 1, q) {
        range(q, h-q, i) {
            range(q, w-q, j) {
                if (m[i][j] == '.')
                    continue;
                i32 a = INT_MAX;
                times(8, k) {
                    i32 y = i + oy[k];
                    i32 x = j + ox[k];
                    if (0 <= y && y < h && 0 <= x && x < w) {
                        a = min(a, v[b][y][x]);
                    }
                }
                v[(b+1)%2][i][j] = a + 1;
                ans = max(ans, a + 1);
            }
        }
        b = (b+1)%2;
    }

    cout << ans << endl;
    return 0;
}