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

const int maxn = 2e3 + 5;
int n, m, sx, sy, ex, ey;
char a[maxn][maxn];
bool v[maxn][maxn];
bool f[maxn][maxn];

const int fx[] = {0, 0, 1, 0, -1};
const int fy[] = {0, 1, 0, -1, 0};
const string d = " >V<^";

struct node {
	int x, y;
	int step;
};

void calc(int x, int y) {
	int i = d.find(a[x][y]), u = 1;
	f[x][y] = false;
	while (true) {
		int tx = x + fx[i] * u;
		int ty = y + fy[i] * u;
		if (tx <= 0 || tx > n || ty <= 0 || ty > m) break;
		if (a[tx][ty] == '#' || d.find(a[tx][ty]) != -1) break;
		f[tx][ty] = false;
		u++;
	}
}

signed main() {
	ios::sync_with_stdio(0);
	cin.tie(0), cout.tie(0);

	cin >> n >> m;
	
	for (int i = 1; i <= n; i++) {
		for (int j = 1; j <= m; j++) {
			cin >> a[i][j];
			if (a[i][j] == 'S') sx = i, sy = j;
			if (a[i][j] == 'G') ex = i, ey = j;
			f[i][j] = true;
		}
	}
	
	for (int i = 1; i <= n; i++) {
		for (int j = 1; j <= m; j++) {
			if (a[i][j] == '#') f[i][j] = false;
			if (d.find(a[i][j]) != -1) {
				f[i][j] = false;
				calc(i, j);
			}
		}
	}
	
	queue<node> q;
	q.push({sx, sy, 0});
	v[sx][sy] = true;
	
	while (q.size() > 0) {
		node u = q.front(); q.pop();
		for (int i = 1; i <= 4; i++) {

      ```int tx = u.x + fx[i];
			int ty = u.y + fy[i];
			
			if (tx <= 0 || tx > n || ty <= 0 || ty > m) continue;
			if (v[tx][ty] == true || f[tx][ty] == false) continue;
			if (tx == ex && ty == ey) {
				cout << u.step + 1 << endl;
				return 0;
			}
			q.push({tx, ty, u.step + 1});
			v[tx][ty] = true;
		}
	}
	
	cout << -1 << endl;
	return 0;
}