kkk1

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.LinkedList;
import java.util.Queue;
import java.util.StringTokenizer;

public class Main {

    static int N, M;
    static char[][] arr;
    static int[] dy = { 0, 1, -1 }, dx = { 1, 1, 1 };

    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(br.readLine());
        N = Integer.parseInt(st.nextToken());
        M = Integer.parseInt(st.nextToken());
        arr = new char[N][M];

        int sy = 0, sx = 0;
        for (int i = 0; i < N; i++) {
            String input = br.readLine();
            for (int j = 0; j < M; j++) {
                char ch = input.charAt(j);
                if (ch == 'R') { // '토끼의 처음위치(y,x) 저장
                    sy = i;
                    sx = j;
                }
                arr[i][j] = ch;
            }
        }

        Queue<Loc> q = new LinkedList<Loc>();
        q.offer(new Loc(sy, sx, 0));
        int ret = -1;

        while (!q.isEmpty()) {
            Loc r = q.poll();

            for (int i = 0; i < 3; i++) {
                int gy = r.y + dy[i];
                int gx = r.x + dx[i];
                if (0 <= gy && gy < N && gx < M) {
                    if (arr[gy][gx] == '#')
                        continue;
                    if (arr[gy][gx] == 'C') {
                        q.add(new Loc(gy, gx, r.c + 1));
                    } else if (arr[gy][gx] == '.') {
                        q.add(new Loc(gy, gx, r.c));
                    } else if (arr[gy][gx] == 'O') {
                        ret = Math.max(ret, r.c);
                    }
                }
            }
        }
        System.out.println(ret);

        br.close();
    }

    static class Loc {
        int y, x, c;

        Loc(int y, int x, int c) {
            this.y = y;
            this.x = x;
            this.c = c;
        }
    }
}