#include <bits/stdc++.h>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>

#define el '\n'
#define FIO ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);

using namespace std;
using namespace __gnu_pbds;

typedef long long ll;
typedef long double ld;
typedef complex<ld> pt;
typedef unsigned long long ull;

template<typename T, typename X>
using hashTable = gp_hash_table<T, X>;
template<typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<typename T>
using ordered_multiset = tree<T, null_type, less_equal<T>, rb_tree_tag, tree_order_statistics_node_update>;

// mt19937_64 for long long
mt19937 rng(std::chrono::system_clock::now().time_since_epoch().count());

const int N = 3e5 + 5;

int n, m;
int dx[] = {1, -1, 0, 0};
int dy[] = {0, 0, -1, 1};

int getId(int i, int j)
{
    return m * i + j;
}

int inDeg[N];
char grid[502][502];
vector<int> shbak[N];
vector<pair<int, int>> G[N];
set<int> G2[N], shbak2[N];

bool valid(int i, int j)
{
    return (i >= 0 && j >= 0 && i < n && j < m);
}

int id;
stack<int> st;
int sz[N], tag[N];
bool vis[N], inStack[N];
vector<int> comp[N], head;
int tin[N], lowLink[N], state[N];

void tarjan(int u)
{
    st.push(u);
    state[u] = 1;
    tin[u] = lowLink[u] = ++id;

    for(auto &[i, j]: G[u])
    {
        int v = getId(i, j);
        if(!state[v])
        {
            tarjan(v);
            lowLink[u] = min(lowLink[u], lowLink[v]);
        }
        else if(state[v] == 1)
            lowLink[u] = min(lowLink[u], tin[v]);
    }

    if(tin[u] == lowLink[u])
    {
        head.push_back(u);
        auto &c = comp[u];
        while(st.top() != u)
        {
            state[st.top()] = 2, tag[st.top()] = u;
            c.push_back(st.top());
            st.pop();
        }
        tag[u] = u;
        c.push_back(u);
        state[u] = 2;
        st.pop();
    }
}

int ans = 0;
map<int, int> mp;

void dfs(int node)
{

    for(auto &it: shbak2[node])
        mp[it]++;

    ans = max(ans, (int) mp.size());
    for(auto &ch: G2[node])
        dfs(ch);

    for(auto &it: shbak2[node])
    {
        mp[it]--;
        if(mp[it] == 0)
            mp.erase(it);
    }
}

void doWork()
{
    cin >> n >> m;
    for(int i = 0; i < n; i++)
        for(int j = 0; j < m; j++)
            cin >> grid[i][j];

    for(int i = 0; i < n; i++)
    {
        for(int j = 0; j < m; j++)
        {
            if(grid[i][j] == '.' || grid[i][j] == '#')
                continue;

            int ni = i, nj = j;
            if(grid[i][j] == '>')
                nj++;
            else if(grid[i][j] == '<')
                nj--;
            else if(grid[i][j] == '^')
                ni--;
            else
                ni++;

            if(valid(ni, nj) && grid[ni][nj] != '.' && grid[ni][nj] != '#')
                G[getId(ni, nj)].emplace_back(i, j);


            for(int k = 0; k < 4; k++)
            {
                ni = i + dx[k], nj = j + dy[k];
                if(valid(ni, nj) && grid[ni][nj] == '#')
                    shbak[getId(i, j)].push_back(getId(ni, nj));
            }
        }
    }


    for(int i = 0; i < n; i++)
    {
        for(int j = 0; j < m; j++)
        {
            if(grid[i][j] == '.' || grid[i][j] == '#' || state[getId(i, j)] == 2)
                continue;
            tarjan(getId(i, j));
        }
    }

    for(int i = 0; i < n * m; i++)
        for(auto &j: G[i])
            G2[tag[i]].insert(tag[getId(j.first, j.second)]), inDeg[tag[getId(j.first, j.second)]]++;


    for(int i = 0; i < n * m; i++)
        for(auto &it: shbak[i])
            shbak2[tag[i]].insert(it);

    for(int i = 0; i < n * m; i++)
    {
        if(inDeg[i] == 0 && G2[i].size())
            dfs(i);
    }
    cout << ans;
}

signed main()
{
    FIO
    int T = 1;
//    cin >> T;
    for(int i = 1; i <= T; i++)
        doWork();
}