#include <bits/stdc++.h>

using namespace std;

struct Move {
    int x, y, count, isknight;
    Move(int x, int y, int count, int isknight) : x(x), y(y), count(count), isknight(isknight) {}
};

int h, w;

bool judge_inside(int x, int y) {
    return x >= 0 && x < w && y >= 0 && y < h;
}

int dx[] = {2, 2, 1, 1, -1, -1, -2, -2};
int dy[] = {1, -1, 2, -2, 2, -2, 1, -1};

int dx2[] = {1, -1, -1, 1};
int dy2[] = {1, 1, -1, -1};

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    cin >> h >> w;
    bool memo[500][500][2];
    vector<string> str(h);
    for (int i = 0; i < h; i++) cin >> str[i];
    int sx, sy, gx, gy;
    for (int i = 0; i < h; i++) {
        for (int j = 0; j < w; j++) {
            if (str[i][j] == 'S') {
                sy = i; 
                sx = j;
            } else if (str[i][j] == 'G') {
                gy = i;
                gx = j;
            }
            for (int k = 0; k < 2; k++) memo[i][j][k] = false;
        }
    }
    queue<Move> q;
    q.push(Move(sx, sy, 0, 1));
    int ans = -1;
    while(!q.empty()) {
        Move m = q.front();
        q.pop();
        if (m.x == gx && m.y == gy) {
            ans = m.count;
            break;
        }
        if (memo[m.y][m.x][m.isknight]) continue;
        memo[m.y][m.x][m.isknight] = true;
        if (str[m.y][m.x] == 'R') m.isknight ^= 1;
        if (m.isknight) {
            for (int i = 0; i < 8; i++) {
                if (!judge_inside(m.x + dx[i], m.y + dy[i])) continue;
                q.push(Move(m.x + dx[i], m.y + dy[i], m.count + 1, 1));
            }
        } else {
            for (int i = 0; i < 4; i++) {
                if (!judge_inside(m.x + dx2[i], m.y + dy2[i])) continue;
                q.push(Move(m.x + dx2[i], m.y + dy2[i], m.count + 1, 0));
            }
        }
    }
    cout << ans << "\n";
    return 0;
}