#pragma GCC optimize("Ofast,unroll-loops")
#include <bits/stdc++.h>
using namespace std;
int n,m;
char s[505][505];
int dx[4]={0,1,0,-1},dy[4]={1,0,-1,0};
int cor[256];
int valid(int x,int y){
    if(x==0||y==0||x>n||y>m) return 0;
    return cor[s[x][y]]!=-1;
}
vector <pair<int,int>> v[505][505],rv[505][505];
int in[505][505],onc[505][505],f[505][505];
vector <pair<int,int>> bl[505][505];
pair<int,int> fa[505][505];
pair<int,int> find(int x,int y){
    return fa[x][y]==make_pair(x,y)?fa[x][y]:fa[x][y]=find(fa[x][y].first,fa[x][y].second);
}
int check(int x,int y){
    if(x==0||y==0||x>n||y>m) return 0;
    return s[x][y]=='#';
}
int ans;
void dfs(int x,int y,int base){
    vector <pair<int,int>> cg;
    for(int i=0;i<4;i++)
        if(check(x+dx[i],y+dy[i])&&!f[x+dx[i]][y+dy[i]])
            f[x+dx[i]][y+dy[i]]++,base++,cg.push_back({x+dx[i],y+dy[i]});
    for(auto t:rv[x][y]){
        if(onc[t.first][t.second]) continue;
        dfs(t.first,t.second,base);
    }
    ans=max(ans,base);
    while(cg.size()) f[cg.back().first][cg.back().second]=0,cg.pop_back();
}
int main() {
    int T = 1, kase = 0;
    //cin >> T;
    while (T--) {
        cin>>n>>m;
        memset(cor,-1,sizeof(cor));
        cor['>']=0,cor['v']=1,cor['<']=2,cor['^']=3;
        for(int i=1;i<=n;i++) scanf("%s",s[i]+1);
        for(int i=1;i<=n;i++)
            for(int j=1;j<=m;j++){
                if(cor[s[i][j]]!=-1&&valid(i+dx[cor[s[i][j]]],j+dy[cor[s[i][j]]]))
                    v[i][j].push_back({i+dx[cor[s[i][j]]],j+dy[cor[s[i][j]]]}),rv[i+dx[cor[s[i][j]]]][j+dy[cor[s[i][j]]]].push_back({i,j}),in[i+dx[cor[s[i][j]]]][j+dy[cor[s[i][j]]]]++;
                else if(cor[s[i][j]]!=-1) v[i][j].push_back({i,j}),rv[i][j].push_back({i,j}),in[i][j]++;
            }
        queue <pair<int,int>> q;
        for(int i=1;i<=n;i++)
            for(int j=1;j<=m;j++)
                onc[i][j]=1;
        for(int i=1;i<=n;i++)
            for(int j=1;j<=m;j++)
                if(cor[s[i][j]]!=-1&&in[i][j]==0)
                    onc[i][j]=0,q.push({i,j});
        while(!q.empty()){
            auto temp=q.front();
            q.pop();
            for(auto t:v[temp.first][temp.second]){
                in[t.first][t.second]--;
                if(!in[t.first][t.second]) q.push({t.first,t.second}),onc[t.first][t.second]=0;
            }
        }
        for(int i=1;i<=n;i++)
            for(int j=1;j<=m;j++)
                if(cor[s[i][j]]!=-1)
                    fa[i][j]={i,j};
        for(int i=1;i<=n;i++)
            for(int j=1;j<=m;j++)
                if(onc[i][j]&&cor[s[i][j]]!=-1){
                    //cout<<i<<" "<<j<<endl;
                    auto x=find(i,j),y=find(v[i][j][0].first,v[i][j][0].second);
                    if(x!=y) fa[y.first][y.second]=x;
                }
        for(int i=1;i<=n;i++)
            for(int j=1;j<=m;j++)
                if(onc[i][j]&&cor[s[i][j]]!=-1)
                    bl[find(i,j).first][find(i,j).second].push_back({i,j});
        for(int i=1;i<=n;i++)
            for(int j=1;j<=m;j++)
                if(onc[i][j]&&cor[s[i][j]]!=-1&&fa[i][j]==make_pair(i,j)){
                    int base=0;
                    for(auto t:bl[i][j]){
                        for(int k=0;k<4;k++)
                            if(check(t.first+dx[k],t.second+dy[k])&&!f[t.first+dx[k]][t.second+dy[k]])
                                f[t.first+dx[k]][t.second+dy[k]]=1,base++;
                    }
                    for(auto t:bl[i][j])
                        dfs(t.first,t.second,base);
                    for(auto t:bl[i][j]){
                        for(int k=0;k<4;k++)
                            if(check(t.first+dx[k],t.second+dy[k]))
                                f[t.first+dx[k]][t.second+dy[k]]=0;
                    }
                }
        printf("%d\n",ans);
    }
    return 0;
}