#include <bits/stdc++.h>
using namespace std;
using ll = long long;

const int H = 502;
const int W = 502;
string arr[H];
int ty[H][W];
int tx[H][W];
int state[H][W];

pair<int, int> dfs(int y, int x, int ind) {
	state[y][x] = ind;
	int ny = ty[y][x];
	int nx = tx[y][x];
	if (arr[ny][nx] == '.' || arr[ny][nx] == '#' || state[ny][nx] == ind) return {y, x};
	if (state[ny][nx] != 0) return {-1, -1};
	return dfs(ny, nx, ind);
}

int revDFS(int y, int x, int& cou) {
	// Activate
	state[y][x] = 1;
	for (int d = 0; d < 4; ++d) {
		int ny = (y - (d == 0) + (d == 2));
		int nx = (x - (d == 1) + (d == 3));
		if (arr[ny][nx] == '#') {
			++state[ny][nx];
			if (state[ny][nx] == 1) ++cou;
		}
	}

	// Recurse
	int res = cou;
	for (int d = 0; d < 4; ++d) {
		int ny = (y - (d == 0) + (d == 2));
		int nx = (x - (d == 1) + (d == 3));
		if (ty[ny][nx] == y && tx[ny][nx] == x) res = max(res, revDFS(ny, nx, cou));
	}

	// Undo
	state[y][x] = 0;
	for (int d = 0; d < 4; ++d) {
		int ny = (y - (d == 0) + (d == 2));
		int nx = (x - (d == 1) + (d == 3));
		if (arr[ny][nx] == '#') {
			--state[ny][nx];
			if (state[ny][nx] == 0) --cou;
		}
	}
	return res;
}

int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(0);

	int h, w;
	cin >> h >> w;
	
	for (int y = 0; y <= h + 1; ++y) arr[y] = string(w + 2, '.');
	for (int y = 1; y <= h; ++y) {
		string tmp;
		cin >> tmp;
		for (int x = 0; x < w; ++x) arr[y][x + 1] = tmp[x];
	}
	h += 2;
	w += 2;

	for (int y = 0; y < h; ++y) {
		for (int x = 0; x < w; ++x) {
			ty[y][x] = y;
			tx[y][x] = x;
			if (arr[y][x] == '<') --tx[y][x];
			if (arr[y][x] == '>') ++tx[y][x];
			if (arr[y][x] == '^') --ty[y][x];
			if (arr[y][x] == 'v') ++ty[y][x];
		}
	}
	
	vector<pair<int, int>> starts;
	for (int y = 1; y + 1 < h; ++y) {
		for (int x = 1; x + 1 < w; ++x) {
			if (arr[y][x] == '.' || arr[y][x] == '#' || state[y][x] != 0) continue;
			pair<int, int> tar = dfs(y, x, y*w + x);
			if (tar.first != -1) starts.push_back(tar);
		}
	}
	for (int y = 0; y < h; ++y) {
		for (int x = 0; x < w; ++x) state[y][x] = 0;
	}

	int res = 0;
	for (int ind = 0; ind < starts.size(); ++ind) {
		int sy = starts[ind].first;
		int sx = starts[ind].second;
		int cou = 0;
		
		for (int y = sy, x = sx; state[y][x] == 0 && arr[y][x] != '.' && arr[y][x] != '#';) {
			state[y][x] = 1;
			for (int d = 0; d < 4; ++d) {
				int ny = (y - (d == 0) + (d == 2));
				int nx = (x - (d == 1) + (d == 3));
				if (arr[ny][nx] == '#') {
					++state[ny][nx];
					if (state[ny][nx] == 1) ++cou;
				}
			}
			
			int ny = ty[y][x];
			int nx = tx[y][x];
			y = ny; x = nx;
		}

		vector<pair<int, int>> ins;
		for (int y = sy, x = sx; state[y][x] == 1 && arr[y][x] != '.' && arr[y][x] != '#';) {
			state[y][x] = 2;
			for (int d = 0; d < 4; ++d) {
				int ny = (y - (d == 0) + (d == 2));
				int nx = (x - (d == 1) + (d == 3));
				if (ty[ny][nx] == y && tx[ny][nx] == x && state[ny][nx] == 0) ins.emplace_back(ny, nx);
			}
			
			int ny = ty[y][x];
			int nx = tx[y][x];
			y = ny; x = nx;
		}

		res = max(res, cou);
		for (auto pr : ins) res = max(res, revDFS(pr.first, pr.second, cou));

		// Undo changes to state
		for (int y = sy, x = sx; state[y][x] != 0 && arr[y][x] != '.' && arr[y][x] != '#';) {
			state[y][x] = 0;
			for (int d = 0; d < 4; ++d) {
				int ny = (y - (d == 0) + (d == 2));
				int nx = (x - (d == 1) + (d == 3));
				if (arr[ny][nx] == '#') --state[ny][nx];
			}
			int ny = ty[y][x];
			int nx = tx[y][x];
			y = ny; x = nx;
		}
	}
	cout << res << '\n';
}