/// Brrrr Brrrr
#pragma GCC optimize("O3")
#pragma GCC optimize ("unroll-loops")
#pragma GCC target("avx,avx2,fma")

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

#define pb push_back
#define F first
#define S second
#define f(i, a, b)  for(int i = a; i < b; i++)
#define all(a)  a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
#define sz(x) (int)(x).size()
#define mp(x,y) make_pair(x,y)
#define popCnt(x) (__builtin_popcountll(x))
//#define int ll

using ll = long long;
using ii = pair<int, int>;
using ull = unsigned long long;

const int N = 1e5+5, LG = 18, MOD = (119 << 23) + 1;
const long double PI = acos(-1);
const long double EPS = 1e-7;

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

int n, m;
char grid[555][555];
vector<vector<ii>> sccs;
vector<ii> g[555][555], rg[555][555];
bool vis[555][555], inCycle[555][555];
int cnt[555][555], cur;
bool isRiver(int i, int j) {
    return grid[i][j] == '>' || grid[i][j] == '<' || grid[i][j] == 'v' || grid[i][j] == '^';
}
bool isRoot(vector<ii> scc) {
    if(scc.size() > 1)
        return 1;
    int i = scc[0].F, j = scc[0].S;
    if(grid[i][j] == '^' && !isRiver(i-1,j))return true;
    if(grid[i][j] == 'v' && !isRiver(i+1,j))return true;
    if(grid[i][j] == '>' && !isRiver(i,j+1))return true;
    if(grid[i][j] == '<' && !isRiver(i,j-1))return true;
    return false;
}

void addEdge(int x1, int y1, int x2, int y2) {
    g[x1][y1].pb({x2,y2});
    rg[x2][y2].pb({x1,y1});
}

vector<ii> stk;
void dfs(int i, int j) {
    vis[i][j] = true;
    for(auto p : g[i][j])
        if(!vis[p.F][p.S])
            dfs(p.F, p.S);
    stk.push_back({i,j});
}
void rdfs(int i, int j) {
    sccs.back().pb({i,j});
    vis[i][j] = true;
    for(auto p : rg[i][j])
        if(!vis[p.F][p.S])
            rdfs(p.F, p.S);
}

void addC(int i, int j, int v) {
    if(grid[i][j] != '#') return;
    cur -= cnt[i][j] > 0;
    cnt[i][j] += v;
    cur += cnt[i][j] > 0;
}
void add(int i, int j, int v) {
    f(k,0,4) {
        int nx = i + dx[k];
        int ny = j + dy[k];
        addC(nx,ny,v);
    }
}
int dfsTree(int i, int j) {
    if(vis[i][j])return 0;
    vis[i][j]=true;
    int ans = 0;
    for(auto v : rg[i][j]) if(!inCycle[v.F][v.S]){
        add(v.F, v.S, +1);
        ans = max(ans, dfsTree(v.F, v.S));
        add(v.F, v.S, -1);
    }

    return max(ans, cur);
}
void doWork() {

    cin >> n >> m;

    int cnt = 0;
    for(int i = 1; i <= n; i++) {
        for(int j = 1; j <= m; j++) {
            cin >> grid[i][j];
            cnt += grid[i][j]=='#';
        }
    }

    for(int i = 1; i <= n; i++) {
        for(int j = 1; j <= m; j++) {
            if(grid[i][j] == '^' && isRiver(i - 1, j))
                addEdge(i,j,i-1,j);
            if(grid[i][j] == 'v' && isRiver(i + 1, j))
                addEdge(i,j,i+1,j);
            if(grid[i][j] == '>' && isRiver(i, j + 1))
                addEdge(i,j,i,j+1);
            if(grid[i][j] == '<' && isRiver(i, j - 1))
                addEdge(i,j,i,j-1);
        }
    }

    for(int i = 1; i <= n; i++)
    for(int j = 1; j <= m; j++)
    if(isRiver(i,j) && !vis[i][j]) {
        dfs(i,j);
    }

    reverse(all(stk));
    memset(vis,0,sizeof vis);

    for(auto p : stk)
    if(!vis[p.F][p.S]) {
        sccs.push_back(vector<ii>());
        rdfs(p.F,p.S);
    }


    int ans = 0;
    memset(vis,0,sizeof vis);
    for(auto c : sccs) if(isRoot(c)){
        if(ans==cnt)break;
        for(auto p : c) {
            inCycle[p.F][p.S]=true;
            add(p.F,p.S,+1);
        }
        for(auto p : c)ans = max(ans, dfsTree(p.F,p.S));
        for(auto p : c)
            add(p.F,p   .S,-1);
    }
    cout << ans << '\n';
}
int32_t main() {
#ifdef ONLINE_JUDGE
    ios_base::sync_with_stdio(0);
    cin.tie(0);
#endif // ONLINE_JUDGE

    int t = 1;
//    cin >> t;
    while (t--) {
        doWork();
    }
    return 0;
}

///Look at my code ya codeomk