#include <bits/stdc++.h>

using namespace std;

#define rng(i,a,b) for(int i=int(a);i<int(b);i++)
#define rep(i,b) rng(i,0,b)
#define repn(i,b) rng(i,1,b+1)
#define gnr(i,a,b) for(int i=int(b)-1;i>=int(a);i--)
#define per(i,b) gnr(i,0,b)
#define pb push_back
#define a first
#define b second
#define eb emplace_back
template<class t>using vc=vector<t>;
template<class t, class u>bool chmin(t &a, u b){
	if(a > b){ a = b; return true;}
	else return false;
}
const int inf = 100000000;

#define mp make_pair
using P=pair<int,int>;
using Q=pair<int,pair<int,P>>;

struct uu{
	vc<int>par,ran;
	void init(int sz){
		par.clear();
		par.resize(sz);
		rep(i, sz) par[i] = i;
		ran.clear();
		ran.resize(sz);
	}
	int find(int x){
		if(x==par[x])return x;
		return par[x]=find(par[x]);
	}
	void unite(int x,int y){
		x=find(x),y=find(y);
		if(x==y)return;
		par[x]=y;
	}
	bool same(int x,int y){
		return find(x)==find(y);
	}
}uf;
int r, c;
string f[505];
int idx, in[260000], out[260000], go[260000];
int cyc[260000], rui[260000];
bool rv[260000];
vc<int>edge[260000];
void dfs(int v,int u){
	in[v] = idx++; 
	for(auto a:edge[v]){
		if(a==u)continue;
		dfs(a,v);
	}
	out[v] = idx-1;
}
void slv(){
	cin>>r>>c;
	rep(i,r)cin>>f[i];
	uf.init(r*c+10);
	vc<P>root;
	rep(i,r){
		rep(j,c){
			int u = i*c+j;
			int v = u;
			bool bad=0; rv[u] = true;
			if(f[i][j]=='^') {
				v-=c;
				if(i==0)bad=1;
			}
			else if(f[i][j]=='v'){
				v+=c;
				if(i==r-1)bad=1;
			}
			else if(f[i][j]=='<'){
				v--;
				if(j==0)bad=1;
			}
			else if(f[i][j]=='>'){
				v++;
				if(j==c-1)bad=1;
			}
			else rv[u] = false;
			if(bad) root.eb(u,-1);
			else if(uf.same(u,v)){
				root.eb(u,v);
			}
			else{
				uf.unite(u,v);
				edge[v].pb(u);
				go[u] = v; 
			}
		}
	}
	memset(cyc,-1,sizeof(cyc));
	for(auto x:root){
		dfs(x.a, -1);
		if(x.b != -1){
			int now = x.b;
			while(1){
				cyc[now] = x.a;
				if(now == x.a) break;
				now = go[now];
			}
		}
	}
	rep(i, r){
		rep(j, c){
			if(f[i][j] != '#') continue;
			vc<P>vec;
			int dx[4]={0,1,0,-1};
			int dy[4]={1,0,-1,0};
			rep(k, 4){
				int nx = i+dx[k];
				int ny = j+dy[k];
				if(0<=nx and 0<=ny and nx<r and ny<c and rv[nx*c+ny]){
					int R = nx*c+ny;
					if(cyc[R] != -1) R = cyc[R];
					vec.eb(in[R], out[R]);
				}
			}
			sort(vec.begin(), vec.end(), [](P a, P b){
				return a.b-a.a > b.b-b.a;
			});
			vc<P>A;
			for(auto uv:vec){
				for(auto nm:A){
					if(nm.a <= uv.a and uv.b <= nm.b) goto nxt;
				}
				A.pb(uv);
				nxt:;
			}
			for(auto uv:A){
				rui[uv.a] ++;
				rui[uv.b+1] --;
			}
		}
	}
	rep(i,260000){
		if(i) rui[i] += rui[i-1];
	}
	int ans=0;
	rep(i,r){
		rep(j,c){
			if(rv[i*c+j]){
				//cout<<i<<" "<<j<<" "<<rui[in[i*c+j]]<<endl;
				ans=max(ans,rui[in[i*c+j]]);
			}
		}
	}
	cout<<ans<<endl;
}	
signed main(){
	cin.tie(0);
	ios::sync_with_stdio(0);
	cout<<fixed<<setprecision(20);
	
	slv();
}