/*
    wa, n^4
*/

#include <bits/stdc++.h>
using namespace std;

const int MN = 505, MD = MN*MN;
const pair<int,int> DIR[4] = {{1,0},{-1,0},{0,1},{0,-1}};
const unordered_map<char,int> MP = {{'v', 0}, {'^', 1}, {'>', 2}, {'<', 3}};

int N, M, sss[MN][MN], nsss=1; char grid[MN][MN]; bool land[MN][MN];
vector<int> ar[MD], radjl[MD]; int adjl[MD], loop[MD], curAns = 0, ans = 0;
bool vis[MD], onSt[MD], curOn[MD], inLoop[MD];

inline pair<int,int> i2p(int i) { --i; return {i/M, i%M}; }
inline int p2i(int r, int c) { return 1 + r*M + c; }
inline bool isIn(int r, int c) { return min(r, c) >= 0 && r < N && c < M; }

void dfs(int u) {
    onSt[u] = vis[u] = 1;
    loop[u] = u;
    if (onSt[adjl[u]]) {
        inLoop[u] = 1;
        for (int v = adjl[u]; v != u; v = adjl[v])
            inLoop[v] = 1, loop[v] = u;
    } else {
        if (!vis[adjl[u]]) dfs(adjl[u]);
    }
    onSt[u] = 0;
}
void dfs2(int u) {
    vector<int> added;
    for (int i: ar[u])
        if (!curOn[i]) {
            curOn[i] = 1;
            ++curAns;
            added.push_back(i);
        }
    // printf("a %d %d\n", u, ans);
    ans = max(ans, curAns);
    for (int v: radjl[u])
        dfs2(v);
    for (int i: added)
        curOn[i] = 0;
    curAns -= added.size();
}

int main() {
    ios_base::sync_with_stdio(0); cin.tie(0);

    cin >> N >> M;
    for (int i = 0; i < N; i++)
        for (int j = 0; j < M; j++) {
            cin >> grid[i][j];
            land[i][j] = grid[i][j] == '#' || grid[i][j] == '.';
            sss[i][j] = grid[i][j] == '#' ? nsss++ : 0;
        }
    for (int i = 0; i < N; i++)
        for (int j = 0; j < M; j++) {
            if (land[i][j]) continue;
            for (auto [dr, dc]: DIR) {
                int r = i+dr, c = j+dc;
                if (isIn(r, c))
                    if (sss[r][c])
                        ar[p2i(i, j)].push_back(sss[r][c]);
            }
            auto [dr, dc] = DIR[MP.at(grid[i][j])];
            int r = i+dr, c = j+dc;
            if (isIn(r, c)) adjl[p2i(i, j)] = p2i(r, c);
        }
    for (int i = 0; i <= N*M; i++)
        if (!vis[i])
            dfs(i);
    for (int i = 0; i <= N*M; i++) {
        if (!inLoop[i])
            radjl[loop[adjl[i]]].push_back(i);
        else
            ar[loop[i]].insert(ar[loop[i]].end(), ar[i].begin(), ar[i].end());
    }
    // for (int i = 0; i <= N*M; i++) {
    //     printf("%d %d: ", loop[i], i);
    //     for (int j: radjl[i]) printf("%d ", j);
    //     printf("\n");
    // }
    for (int i = 0; i <= N*M; i++)
        if (inLoop[i] && i == loop[i])
            dfs2(i);
    printf("%d\n", ans);


    return 0;
}