#include <bits/stdc++.h>
using namespace std;
#define debug(x) cerr << #x << " == " << x << endl
#define FINISH cerr << "FINISH!!!!" << endl;
#define el '\n'
#define fir first
#define sec second
typedef long long ll;
typedef pair<int, int> PII;
const int mod = 1000000007;
const int inf = 0x3f3f3f3f;
const int N = 550;
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};
void solve()
{
	int h, w, tot = 0;
	cin >> h >> w;
	vector<vector<char>> ch(h + 2, vector<char>(w + 2, '*'));
	vector<vector<int>> idx(h + 2, vector<int>(w + 2, 0));
	vector<int> col((h + 2) * (w + 2), 0);
	for (int i = 1; i <= h; i++) {
		for (int j = 1; j <= w; j++) {
			cin >> ch[i][j];
			if (ch[i][j] == 'V' || ch[i][j] == 'H') {
				tot++;
				idx[i][j] = tot;
				col[tot] = (ch[i][j] == 'H') ? 1 : 0;
			}
		}
	}
	/*for (int i = 0; i <= h + 1; i++) {
		for (int j = 0; j <= w + 1; j++) {
			cout << ch[i][j];
		}
		cout << endl;
	}*/
	vector<vector<vector<int>>> edge(2, vector<vector<int>>(tot + 3));
	function<PII(int, int, int, int)> search = [&](int x, int y, int dx,
												   int dy) {
		int nowx = x, nowy = y, cnt = 0;
		// cout << x << " " << y << " " << dx << " " << dy << endl;
		while (1) {
			nowx += dx, nowy += dy;
			// cout << nowx << " " << nowy << endl;
			if (ch[nowx][nowy] == '#')
				break;
			if (ch[nowx][nowy] == '\\') {
				swap(dx, dy);
				// nowx += dx, nowy += dy;
				cnt++;
			}
			else if (ch[nowx][nowy] == '/') {
				swap(dx, dy);
				dx = -dx, dy = -dy;
				// nowx += dx, nowy += dy;
				cnt++;
			}
			else if (ch[nowx][nowy] == '*') {
				dx = -dx, dy = -dy;
				// nowx += dx, nowy += dy;
			}
			if (ch[nowx][nowy] == 'H' || ch[nowx][nowy] == 'V') {
				// cout << nowx << " " << nowy << endl;
				if (cnt % 2 == 1) {
					// edge1[idx[x][y]].push_back(idx[nowx][nowy]);
					// edge1[idx[nowx][nowy]].push_back(idx[x][y]);
					return PII(idx[nowx][nowy], 1);
					// cout << x << " " << y << " " << nowx << " " << nowy << "
					// "
					// 	 << "1" << endl;
				}
				else {
					// edge0[idx[x][y]].push_back(idx[nowx][nowy]);
					// edge0[idx[nowx][nowy]].push_back(idx[x][y]);
					return PII(idx[nowx][nowy], 0);
					// cout << x << " " << y << " " << nowx << " " << nowy << "
					// "
					// 	 << "0" << endl;
				}
			}
		}
		return PII(-1, -1);
		// cout << "FINISH" << endl;
	};
	vector<vector<int>> prohibit(tot + 3, vector<int>(2, 0));
	function<void(int, int)> dfs = [&](int x, int y) {
		int dx, dy;
		PII res1 = search(x, y, 1, 0), res2 = search(x, y, -1, 0);
		if (res1.fir != -1 && res2.fir != -1) {
			edge[res1.sec][idx[x][y]].push_back(res1.fir);
			edge[res1.sec][res1.fir].push_back(idx[x][y]);
			edge[res2.sec][idx[x][y]].push_back(res2.fir);
			edge[res2.sec][res2.fir].push_back(idx[x][y]);
			/*cout << idx[x][y] << " " << res1.fir << endl;
			cout << x << " " << y << " " << place[res1.fir].fir << " "
				 << place[res1.fir].sec << " " << res1.sec << endl;
			cout << idx[x][y] << " " << res2.fir << endl;
			cout << x << " " << y << " " << place[res2.fir].fir << " "
				 << place[res2.fir].sec << " " << res2.sec << endl;*/
			prohibit[idx[x][y]][0] = 1;
		}
		res1 = search(x, y, 0, 1), res2 = search(x, y, 0, -1);
		if (res1.fir != -1 && res2.fir != -1) {
			edge[res1.sec][idx[x][y]].push_back(res1.fir);
			edge[res1.sec][res1.fir].push_back(idx[x][y]);
			edge[res2.sec][idx[x][y]].push_back(res2.fir);
			edge[res2.sec][res2.fir].push_back(idx[x][y]);
			/*cout << idx[x][y] << " " << res1.fir << endl;
			cout << x << " " << y << " " << place[res1.fir].fir << " "
				 << place[res1.fir].sec << " " << res1.sec << endl;
			cout << idx[x][y] << " " << res2.fir << endl;
			cout << x << " " << y << " " << place[res2.fir].fir << " "
				 << place[res2.fir].sec << " " << res2.sec << endl;*/
			prohibit[idx[x][y]][1] = 1;
		}
	};
	for (int i = 1; i <= h; i++) {
		for (int j = 1; j <= w; j++) {
			if (ch[i][j] == 'H' || ch[i][j] == 'V') {
				// cout << i << " " << j << endl;
				dfs(i, j);

				if (prohibit[idx[i][j]][0] == 0 &&
					prohibit[idx[i][j]][1] == 0) {
					cout << "-1" << endl;
					return;
				}
			}
		}
	}
	// FINISH
	vector<vector<int>> block(tot + 3);
	vector<int> vis(tot + 3, 0);
	function<void(int, int)> find = [&](int x, int res) {
		if (vis[x])
			return;
		vis[x] = res;
		block[res].push_back(x);
		for (auto to : edge[0][x]) {
			if (vis[to])
				continue;
			find(to, res);
		}
	};
	int now = 0;
	for (int i = 1; i <= tot; i++) {
		if (!vis[i])
			find(i, ++now);
	}
	// 0->V 1->H
	/*for (int i = 1; i <= tot; i++) {
		cout << col[i] << endl;
		cout << prohibit[i][0] << " " << prohibit[i][1] << endl;
	}*/
	int ans = 0;
	int cnt = 0;
	vector<vector<int>> val(tot + 3, vector<int>(2, 0));
	for (int i = 1; i <= now; i++) {
		// debug(i);
		int cnt0 = 0, cnt1 = 0;
		for (auto x : block[i]) {
			// cout << x << " ";
			if (prohibit[x][0] == 0) {
				cnt0 = inf;
			}
			if (prohibit[x][1] == 0) {
				cnt1 = inf;
			}
			if (cnt0 <= inf && col[x] == 1)
				cnt0++;
			if (cnt1 <= inf && col[x] == 0)
				cnt1++;
		}
		val[i][0] = cnt0;
		val[i][1] = cnt1;
		if (cnt0 <= inf)
			cnt += cnt0;
		if (cnt1 <= inf)
			cnt += cnt1;
		/*cout << endl;
		cout << val[i][0] << " " << val[i][1] << endl;*/
	}
	// cout << cnt << endl;
	// assert(cnt <= tot * 2);
	/*for (int i = 1; i <= tot; i++) {
		cout << vis[i] << " ";
	}
	cout << endl;*/
	vector<vector<int>> edge1(tot + 3);

	for (int i = 1; i <= now; i++) {
		vector<int> fl(tot + 3, 0);
		for (auto x : block[i]) {
			cnt++;
			for (auto to : edge[1][x]) {
				if (vis[x] != vis[to] && fl[vis[to]] == 0) {
					fl[vis[to]] = 1;
					edge1[i].push_back(vis[to]);
					// edge1[vis[to]].push_back(i);
				}
				if (vis[x] == vis[to]) {
					cout << "-1" << endl;
					return;
				}
			}
		}
	}

	/*FINISH
	for (int i = 1; i <= now; i++) {
		for (auto to : edge1[i]) {
			cout << "EDGE" << i << " " << to << endl;
		}
	}*/
	int ans1 = 0, ans2 = 0;
	vector<int> las, lt;
	vector<int> tmp(tot + 3, 0);
	function<int(int, int)> getcol = [&](int x, int c) -> int {
		// cout << "getcol   " << x << endl;
		vis[x] = 1, col[x] = c;
		las.push_back(x);
		int sum = val[x][c], flag = 0;
		tmp[x]++;
		for (int to : edge1[x]) {
			if (vis[to]) {
				// cout << x << " " << to << endl;
				// cout << col[x] << " " << col[to] << endl;
				if (col[to] == col[x]) {
					flag = 1;
				}
				continue;
			}
			int noww = getcol(to, c ^ 1);
			if (noww == -1)
				flag = 1;
			sum += noww;
		}
		if (flag != 1)
			return sum;
		return -1;
	};
	for (int i = 1; i <= now; i++) {
		vis[i] = col[i] = 0;
	}
	for (int i = 1; i <= now; i++) {
		int sum1 = 0, sum2 = 0;
		// debug(i);
		if (vis[i])
			continue;
		sum1 = getcol(i, 0);
		if (sum1 == -1) {
			// cout << i << endl;
			cout << "-1" << endl;
			return;
		}
		// cout << "LAS" << endl;
		for (auto x : las) {
			// cout << x << " ";
			vis[x] = col[x] = 0;
			lt.push_back(x);
		}
		// cout << endl;
		las.clear();
		sum2 = getcol(i, 1);
		// cout << sum1 << " " << sum2 << endl;
		ans1 += min(sum1, sum2);
		las.clear();
		/*cout << "VIS" << endl;
		for (int j = 1; j <= 3; j++)
			cout << vis[j] << " ";
		cout << endl;
		cout << ans1 << endl;*/
	}
	if (ans1 >= inf)
		ans1 = -1;
	cout << ans1 << endl;
}
int main()
{
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	cout.tie(nullptr);
	int T = 1;
	// cin >> T;
	while (T--) {
		solve();
	}
	return 0;
}