#include <bits/stdc++.h>
#define pb push_back
#define ott(i,l,r) for (int i = l; i <= r; i ++)
#define tto(i,l,r) for (int i = r; i >= l; i --)
using namespace std;
int read () {
	int x = 0; bool f = false; char c = getchar ();
	while (!isdigit (c)) f |= (c == '-'), c = getchar ();
	while (isdigit (c)) x = (x << 3) + (x << 1) + (c ^ 48), c = getchar ();
	return f ? -x : x;
}
typedef long long ll;
const int N = 2200;
int n, m, c, bc, wc, tot, cnt;
ll res; int id[N][N], dx[4] = {-1, 1, 0, 0}, dy[4] = {0, 0, -1, 1};
bool vis[N], ok[N][N]; char s[N]; int bl[N];
vector <pair <int, int> > b, w;
vector <int> e[N];
bool match (int u) {
	for (int v : e[u]) {
		if (vis[v]) continue; vis[v] = true;
		if (!bl[v] || match (bl[v])) return bl[v] = u, true;
	}
	return false;
}
void dfs (int z, int u) {
	for (int v : e[u]) {
        if (vis[v]) continue; vis[v] = true;
        ok[z][v] = true; dfs (z, bl[v]);
    }
    return ;
}
int main () {
	n = read (), m = read ();
	ott (i, 1, n) {
		scanf ("%s", s + 1);
		ott (j, 1, m) {
			if (s[j] ^ '.') continue;
			if (i + j & 1) b.pb ({i, j}), id[i][j] = ++ bc;
			else w.pb ({i, j}), id[i][j] = ++ wc;
		}
	}
	res = 1ll * bc * (bc - 1) / 2ll + 1ll * wc * (wc - 1) / 2ll;
	if (res >= 1e6) return puts ("1000000"), 0;
	// printf ("%lld\n", res);
	for (auto [x, y] : b) {
		int u = id[x][y];
		ott (i, 0, 3) {
			int v = id[x + dx[i]][y + dy[i]];
			if (v) e[u].pb (v);
		}
	}
	for (auto [x, y] : b) {
		fill (vis + 1, vis + 1 + wc, false);
		if (match (id[x][y])) ++ c;
	}
	assert (c == bc);
	for (auto [x, y] : b) {
		fill (vis + 1, vis + 1 + wc, false);
		dfs (id[x][y], id[x][y]);
	}
	ott (u, 1, bc)
	    ott (v, 1, wc)
	        if (!ok[u][v])
	        	++ res;
	if (res >= 1e6) res = 1e6;
	printf ("%lld\n", res);
	return 0;
}