#include <bits/stdc++.h>

using namespace std;

set<int> bins;
int r,c; 
int dr[4] = {0,0,1,-1};
int dc[4] = {1,-1,0,0};
map<char, int> dir = {{'>', 0}, {'<', 1}, {'v', 2}, {'^', 3}, {'.', -1}, {'#', -1}};
int inv[300000] = {};
vector<int> cycidx(300000, -1);

vector<int> nxt(300000, -1000000);
set<int> adjbins[300000];
vector<set<int>> cycbins;
int numcyc = 0;
int vis[300000] = {};
int ans = 0;

set<int> currbins;

int to_idx(int i, int j) {
    return (c+2) * i + j;
}

void dfs(int u) {
    if(vis[u] == 2) return;
    if(vis[u] == 1) {
        int v = nxt[u];
        vector<int> cyc = {u};
        while(v != u) {
            cyc.push_back(v);
            v = nxt[v];
        }
        set<int> cbins;
        for(auto x : cyc) {
            for(auto b : adjbins[x]) {
                cbins.insert(b);
            }
            cycidx[x] = numcyc;
        }
        cycbins.push_back(cbins);
        numcyc++;
        return;
    }
    vis[u] = 1;
    if(nxt[u] != -1000000) dfs(nxt[u]);
    vis[u] = 2;
    return;
}

void dfs2(int u) {
  //  cout << "U " << u << endl;
    if(cycidx[u] != -1) {
 //       cout << u << " " << cycidx[u] << " " << cycbins.size() << endl;
        for(int b : cycbins[cycidx[u]]) currbins.insert(b);
        return;
    }
    

    if(nxt[u] != -1000000) {
        for(int b : adjbins[u]) currbins.insert(b);
        dfs2(nxt[u]);
    }
}


int main() {
    cin.tie(0)->sync_with_stdio(0);
    cin >> r >> c;
    char g[510][510] = {};
    for(int i = 1; i <= r; i++) {
        for(int j = 1; j <= c; j++) {
            cin >> g[i][j];
            if(g[i][j] == '#') bins.insert(to_idx(i,j));
        }
    }

    for(int i = 1; i <= r; i++) {
        for(int j = 1; j <= c; j++) {
            int d = dir[g[i][j]];
            int idx = to_idx(i,j);
            if(d >= 0) {
                int ni = i + dr[d];
                int nj = j + dc[d];
                int nidx = to_idx(ni, nj);
                inv[nidx]++;
                nxt[idx] = nidx;

                for(int k = 0; k < 4; k++) {
                    int ki = i + dr[k];
                    int kj = j + dc[k];
                    int kidx = to_idx(ki, kj);
                    if(bins.count(kidx)) adjbins[idx].insert(kidx);
                }
            }
        }
    }

    for(int i = 1; i <= r; i++) {
        for(int j = 1; j <= c; j++) {
            int idx = to_idx(i,j);
            if(vis[idx] == 0 && nxt[idx] != -1000000) {
                dfs(idx);
            }
        }
    }

    for(int i = 1; i <= r; i++) {
        for(int j = 1; j <= c; j++) {
            int idx = to_idx(i,j);
            vis[idx] = 0;
        }
    }


    for(int i = 1; i <= r; i++) {
        for(int j = 1; j <= c; j++) {
            int idx = to_idx(i,j);
            if(inv[idx] == 0 && nxt[idx] != -1000000) {
                currbins.clear();
                dfs2(idx);
                ans = max(ans, (int) currbins.size());
            }

        }
    }

    for(auto x : cycbins) {
        ans = max(ans, (int) x.size());
    }

    cout << ans << endl;

    
    return 0;
}