#include <cassert>
#include <cmath>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <functional>
#include <iostream>
#include <limits>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;

using Int = long long;

template <class T1, class T2> ostream &operator<<(ostream &os, const pair<T1, T2> &a) { return os << "(" << a.first << ", " << a.second << ")"; };
template <class T> ostream &operator<<(ostream &os, const vector<T> &as) { const int sz = as.size(); os << "["; for (int i = 0; i < sz; ++i) { if (i >= 256) { os << ", ..."; break; } if (i > 0) { os << ", "; } os << as[i]; } return os << "]"; }
template <class T> void pv(T a, T b) { for (T i = a; i != b; ++i) cerr << *i << " "; cerr << endl; }
template <class T> bool chmin(T &t, const T &f) { if (t > f) { t = f; return true; } return false; }
template <class T> bool chmax(T &t, const T &f) { if (t < f) { t = f; return true; } return false; }
#define COLOR(s) ("\x1b[" s "m")


int M, N;
char A[60][60];

int mod(int x, int m) {
  return ((x %= m) < 0) ? (x + m) : x;
}

int dist[2510][60][60];

int main() {
  for (; ~scanf("%d%d", &M, &N); ) {
    for (int x = 0; x < M; ++x) {
      scanf("%s", A[x]);
    }
    
    const int L = M / __gcd(M, N) * N;
    
    queue<pair<int, pair<int, int>>> que;
    memset(dist, ~0, sizeof(dist));
    dist[0][0][0] = 0;
    que.emplace(0, make_pair(0, 0));
    for (; que.size(); ) {
      const int r = que.front().first;
      const int x = que.front().second.first;
      const int y = que.front().second.second;
      que.pop();
      auto visit = [&](int rr, int xx, int yy) -> void {
        if (rr >= L) rr -= L;
        xx = mod(xx, M);
        yy = mod(yy, N);
        if (!~dist[rr][xx][yy]) {
          dist[rr][xx][yy] = dist[r][x][y] + 1;
          que.emplace(rr, make_pair(xx, yy));
        }
      };
      if (A[mod(x - r, M)][y] == 'v') visit(r + 1, x + 1, y);
      if (A[mod(x + r, M)][y] == '^') visit(r + 1, x - 1, y);
      if (A[x][mod(y - r, N)] == '>') visit(r + 1, x, y + 1);
      if (A[x][mod(y + r, N)] == '<') visit(r + 1, x, y - 1);
    }
    
    int ans = -1;
    for (int r = 0; r < L; ++r) {
      const int d = dist[r][M - 1][N - 1];
      if (~d) {
        if (!~ans || ans > d) ans = d;
      }
    }
    printf("%d\n", ans);
  }
  return 0;
}