#include <bits/stdc++.h>
#define ll long long
#define pii pair<int, int>
#define pll pair<ll, ll>
#define pdd pair<double, double>
#define F first
#define S second
#define all(x) x.begin(), x.end()

using namespace std;

const double eps = 1e-9;

int r, c, n, m, visg[505][505], idx[505][505];
int vist[250005], in[250005], ans;
char g[505][505];
vector<int> E[250005];
vector<int> sp[250005];

bool is_river(int i, int j)
{
    return "^v<>"s.find(g[i][j]) != string::npos;
}

pii delta(char ch)
{
    int dx = 0, dy = 0;
    if (ch == '^')
        dx = -1;
    else if (ch == 'v')
        dx = 1;
    else if (ch == '<')
        dy = -1;
    else if (ch == '>')
        dy = 1;
    return pii(dx, dy);
}

void cycle(int i, int j, int id)
{
    visg[i][j] = 2;
    idx[i][j] = id;
    auto [dx, dy] = delta(g[i][j]);
    if (visg[i + dx][j + dy] == 1)
        cycle(i + dx, j + dy, id);
}

void dfs(int i, int j)
{
    visg[i][j] = 1;
    auto [dx, dy] = delta(g[i][j]);
    if (is_river(i + dx, j + dy))
    {
        if (visg[i + dx][j + dy] == 0)
            dfs(i + dx, j + dy);
        else if (visg[i + dx][j + dy] == 1)
            cycle(i + dx, j + dy, ++n);
    }
    else 
        cycle(i, j, ++n); // mark myself a self-loop
    visg[i][j] = 2;
}

void dfstree(int u, int acc)
{
    vist[u] = 1;
    for (auto i : sp[u])
        if (in[i]++ == 0)
            acc++;
    ans = max(ans, acc);
    for (auto v : E[u])
        if (!vist[v]) // can be a self loop
            dfstree(v, acc);
    for (auto i : sp[u])
        --in[i];
}

signed main()
{
    ios::sync_with_stdio(0);
    cin.tie(0), cout.tie(0);
    cin >> r >> c;
    for (int i = 1; i <= r; i++)
        for (int j = 1; j <= c; j++)
            cin >> g[i][j];
            
    for (int i = 1; i <= r; i++)
        for (int j = 1; j <= c; j++)
            if (is_river(i, j) && !visg[i][j])
                dfs(i, j);
    for (int i = 1; i <= r; i++)
        for (int j = 1; j <= c; j++)
            if (is_river(i, j))
            {
                if (!idx[i][j])
                    idx[i][j] = ++n;
            }
            else if(g[i][j] == '#')
                idx[i][j] = ++m;

    for (int i = 1; i <= r; i++)
        for (int j = 1; j <= c; j++)
            if (is_river(i, j))
            {
                auto [dx, dy] = delta(g[i][j]);
                if (is_river(i + dx, j + dy))
                    E[idx[i + dx][j + dy]].emplace_back(idx[i][j]);
            }
            else if (g[i][j] == '#')
            {
                for (auto ch : "^v<>")
                {
                    auto [dx, dy] = delta(ch);
                    if (is_river(i + dx, j + dy))
                        sp[idx[i + dx][j + dy]].emplace_back(idx[i][j]);
                }
            }
    for (int i = 1; i <= n; i++)
        if (!vist[i])
            dfstree(i, 0);
    cout << ans << '\n';
}