#include <iostream>     // Input/output stream objects
#include <fstream>      // File stream objects
#include <sstream>      // String stream objects
#include <iomanip>      // Input/output manipulators
#include <string>       // String class and functions
#include <vector>       // Dynamic array
#include <list>         // Doubly linked list
#include <set>          // Set container
#include <map>          // Map container
#include <queue>        // Queue container
#include <stack>        // Stack container
#include <algorithm>    // Algorithms on sequences (e.g., sort, find)
#include <cmath>        // Mathematical functions
#include <climits>      // LLONG_MAX, LLONG_MIN
#include <ctime>        // Date and time functions
#include <cstdlib>      // General purpose functions (e.g., memory management)
#include <cstring>      // C-style string functions
#include <cctype>       // Character classification functions
#include <cassert>      // Assert function for debugging
#include <exception>    // Standard exceptions
#include <functional>   // Function objects
#include <iterator>     // Iterator classes
#include <limits>       // Numeric limits
#include <locale>       // Localization and internationalization
#include <numeric>      // Numeric operations (e.g., accumulate)
#include <random>       // Random number generators
#include <stdexcept>    // Standard exception classes
#include <typeinfo>     // Runtime type information
#include <utility>      // Utility components (e.g., std::pair)
#include <bitset>

using namespace std;

#define FOR(i, a, b) for(int i = a; i < (b); i++)
#define FORE(i, a, b) for(int i = a; i <= (b); i++)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
#define x first 
#define y second
#define mp make_pair
#define PI 3.141592653
#define compress(coord) sort(all(coord)), coord.resize(unique(all(coord)) - coord.begin())
const double eps = 1e-9; // x < eps (x <= 0) x < -eps (x < 0)
const ll inf = LLONG_MAX;

const int N = 510;
int n, m, sight, ans;

vector<string> ter(N), rter;
vector<vi> vis(N, vi(N, 0)), instack(N, vi(N, 0)), cnt(N, vi(N, 0)), chk(N, vi(N, 0));
vector<pii> en, sta, dis({{0, 1}, {0, -1}, {1, 0}, {-1, 0}});
vector<vector<pii>> cyc;

bool iswater(char c) { return c != '.' && c != '#'; }

pii find_di(char c) {
    if (c == '<') return mp(0, -1);
    else if (c == '>') return mp(0, 1);
    else if (c == '^') return mp(-1, 0);
    return mp(1, 0);
}

bool out(int ti, int tj) { 
    if (ti >= n || ti < 0 || tj >= m || tj < 0) return true; 
    return false;
}

void dfs(int i, int j) {
    sta.push_back(mp(i, j));
    vis[i][j] = 1;
    pii di = find_di(ter[i][j]);
    int ti = i + di.x, tj = j + di.y;
    if (out(ti, tj) || !iswater(ter[ti][tj]) || vis[ti][tj] == 2) {
        vis[i][j] = 2;
        sta.pop_back();
        return ;
    }
    
    if (vis[ti][tj] == 1) {
        vector<pii> curcy;       
        int curid = sz(sta) - 1;
        while (curid >= 0 && sta[curid].x != ti || sta[curid].y != tj) {
            curcy.push_back(sta[curid]);
            curid--;   
        }
        curcy.push_back(mp(ti, tj));
        cyc.push_back(curcy);
    }
    else dfs(ti, tj);
    
    vis[i][j] = 2;
    sta.pop_back();
} 

bool tous(int i, int j, pii di) {
    int ti = di.x + i, tj = di.y + j;
    if (out(ti, tj) || !iswater(ter[ti][tj])) return false;
    pii ret = find_di(ter[ti][tj]);
    if (ti + ret.x == i && tj + ret.y == j) return true; 
    return false;
}

void push(int i, int j) {
    // cout << "PUSH " << i << " " << j << endl;
    chk[i][j] = 1;
    for (pii di: dis) {
        int ti = di.x + i, tj = di.y + j; // check 4 direction
        if (out(ti, tj)) continue; 
        if (ter[ti][tj] == '#') {
            cnt[ti][tj]++;
            if (cnt[ti][tj] == 1) sight++;
        }
    }

    ans = max(ans, sight);
    for (pii di: dis) if (tous(i, j, di)) push(i + di.x, j + di.y);

    // return from push
    for (pii di: dis) {
        int ti = di.x + i, tj = di.y + j; // check 4 direction
        if (out(ti, tj)) continue; 
        if (ter[ti][tj] == '#') { 
            cnt[ti][tj]--;
            if (cnt[ti][tj] == 0) sight--;
        }
    }
    return ;
}

int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
    cin >> n >> m;
    FOR(i, 0, n) cin >> ter[i];

    FOR (i, 0, n) FOR (j, 0, m) if (vis[i][j] == 0 && iswater(ter[i][j])) dfs(i, j);

    // cout << "NUM CYC" << sz(cyc) << endl;
    for (vector<pii> cy: cyc) {
        // cout << "CYC: " << endl;
        vector<pii> tosolve;
        sight = 0; // global
        for (int i = 0; i < sz(cy); i++) {
            pii temp = cy[i], prev = cy[(i-1+sz(cy)) % sz(cy)], nxt = cy[(i+1)%sz(cy)];
            // cout << "(" << temp.x << ", " << temp.y << ")";
            chk[temp.x][temp.y] = 1;
            for (pii di: dis) {
                int ti = di.x + temp.x, tj = di.y + temp.y; // check 4 direction
                if (out(ti, tj)) continue; 
                if (ter[ti][tj] == '#') {
                    cnt[ti][tj]++;
                    if (cnt[ti][tj] == 1) sight++;
                }
            }
            
            for (pii di: dis) {
                int ti = di.x + temp.x, tj = di.y + temp.y; // check 4 direction
                if (tie(ti, tj) == tie(prev.x, prev.y) || tie(ti, tj) == tie(nxt.x, nxt.y)) continue ; // in cycle
                if (tous(temp.x, temp.y, di)) tosolve.push_back(mp(temp.x + di.x, temp.y + di.y));
            }
        }
        ans = max(ans, sight);

        // cout << "TOSOLVE: ";
        // for (pii st: tosolve) {
        //     cout << st.x << " " << st.y << endl;
        // }
        for (pii st: tosolve) push(st.x, st.y);

        // clear
        for (int i = 0; i < sz(cy); i++) {
            pii temp = cy[i];
            for (pii di: dis) {
                int ti = di.x + temp.x, tj = di.y + temp.y; // check 4 direction
                if (out(ti, tj)) continue; 
                if (ter[ti][tj] == '#') cnt[ti][tj]--;
            }
        }
        // cout << endl;
    } 

    cnt = vector<vi>(N, vi(N, 0));
    FOR (i, 0, n) FOR (j, 0, m) if (chk[i][j] == 0 && iswater(ter[i][j])) {
        int di, dj;
        tie(di, dj) = find_di(ter[i][j]);

        int ti = i + di, tj = j + dj; 

        if (out(ti, tj) || !iswater(ter[ti][tj])) {
            // cout << "ENDPOINT: " << i << " " << j << " " << ter[i][j] << endl;
            sight = 0;
            push(i, j);
        }
    }   
    cout << ans << endl;
}