#include<bits/stdc++.h>

using namespace std;

const int maxn = 510;

int n, m; 
int st[maxn][maxn], dx[maxn][maxn], dy[maxn][maxn];
int vis[maxn][maxn], used[maxn][maxn], is_cycle[maxn][maxn], now;

int mx, ax, ay;

vector<pair<int, int>>G[maxn][maxn];

void move(int &tx, int &ty) {
    auto ddx = dx[tx][ty];
    auto ddy = dy[tx][ty];
    tx += ddx;
    ty += ddy;
}

vector<pair<int, int>>add(int x, int y) {
    vector<pair<int, int>>ans;
    if(st[x-1][y]==-1 and used[x-1][y]==0) {
        ans.push_back({x-1, y});
        used[x-1][y] = 1;
    }
    if(st[x+1][y]==-1 and used[x+1][y]==0) {
        ans.push_back({x+1, y});
        used[x+1][y] = 1;
    }
    if(st[x][y-1]==-1 and used[x][y-1]==0) {
        ans.push_back({x, y-1});
        used[x][y-1] = 1;
    }
    if(st[x][y+1]==-1 and used[x][y+1]==0) {
        ans.push_back({x, y+1});
        used[x][y+1] = 1;
    }
    return ans;
}

void dfs(int x, int y) {
    vis[x][y] = 1;
    //cout << x << ' ' << y << ' ' << now << endl;
    if(now>mx) {
        mx = now;
        ax = x, ay = y;
    }
    for(auto &[sx, sy]: G[x][y]) {
        if(is_cycle[sx][sy]) continue;
        auto vec = add(sx, sy);
        now += vec.size();
        dfs(sx, sy);
        now -= vec.size();
        for(auto &[a, b]: vec) {
            used[a][b] = false;
        }
    }
}

void solve() {
    cin >> n >> m;
    for(int i = 1; i <= n ; i ++) {
        string s; cin >> s;
        for(int j = 1 ; j <= m ;j ++) {
            if(s[j-1]=='.') st[i][j] = 0;
            else if(s[j-1]=='#') st[i][j] = -1;
            else {
                st[i][j] = 1;
                if(s[j-1]=='^') dx[i][j] = -1, dy[i][j] = 0;    
                else if(s[j-1]=='v') dx[i][j] = 1, dy[i][j] = 0;
                else if(s[j-1]=='<') dx[i][j] = 0, dy[i][j] = -1;
                else dx[i][j] = 0, dy[i][j] = 1;
            }
        }
    }
    for(int i = 1 ; i <= n ; i ++) {
        for(int j = 1 ; j <= m ; j ++) {
            if(st[i][j]!=1) continue;
            int nx = i+dx[i][j], ny = j+dy[i][j];
            G[nx][ny].push_back({i, j});
            //cout << i << ' ' << j << ' ' << nx << ' ' << ny << endl;
        }
    }
    for(int i = 1 ; i <= n ; i ++) {
        for(int j = 1 ;j <= m ; j ++) {
            if(vis[i][j]) continue;
            int tx = i, ty = j;

            // cout << "point1" << endl;

            bool flag = false;
            while(true) {
                // find a circle
                if(vis[tx][ty]) {
                    flag = true;
                    break;
                }
                // land or sight
                if(st[tx][ty]!=1) break;
                vis[tx][ty] = true;
                move(tx, ty);
            }
            
            // for a cycle(cactus)
            if(flag) {
                vector<pair<int, int>>path;
                while(true) {
                    if(!path.empty() and *path.begin()==pair<int, int>{tx, ty}) {
                        break;
                    }
                    is_cycle[tx][ty] = 1;
                    path.push_back({tx, ty});
                    move(tx, ty);
                }

                now = 0;
                vector<pair<int, int>>backup;
                for(auto &[a, b]: path) {
                    auto vec = add(a, b);
                    now += vec.size();
                    backup.insert(backup.end(), vec.begin(), vec.end());
                }
                // cout << "point3" << endl;
                for(auto &[a, b]: path) {
                    dfs(a, b);
                }
                // cout << "point5" << endl;
                for(auto &[a, b]: backup) {
                    used[a][b] = false;
                }
                now = 0;
            }
            // for a tree
            else {
                // cout << "point4" << endl;
                dfs(tx, ty);
            }
        }
    }
    cout << mx << endl;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    solve();

    return 0;
}