#include <iostream>
#include <vector>
#include<queue>
#include <algorithm>
using namespace std;
int main() {
int H, W;
cin >> H >> W;
cin.ignore();
vector<vector<char>> mapp(H, vector<char>(W));
for (int i=0; i<H; i++) {
string line;
cin >> line;
for (int j=0; j<W; j++) {
mapp[i][j] = line[j];
}
}
vector<char> ani(2, '.');
if (mapp[0][0] == 'R') ani = {'R', 'F'};
else ani = {'F', 'R'};
int dirs[4][2] = { {0,1}, {1,0}, {0,-1}, {-1,0} };
int count = 0;
bool flag0 = false, flag1 = false;
vector<vector<int>> vis(H, vector<int>(W, 0));
int vid = 1; // visit ID trick
while(true) {
flag0 = false;
flag1 = false;
deque<pair<int, int>> q;
q.push_back({0,0});
vis[0][0] = vid;
while (!q.empty()) {
auto [r, c] = q.front();
q.pop_front();
for (int i = 0; i < 4; i++) {
int rr = r + dirs[i][0];
int cc = c + dirs[i][1];
if (rr < 0 || rr >= H || cc < 0 || cc >= W) continue;
if (vis[rr][cc] == vid) continue;
if (mapp[rr][cc] == '.') continue;
if (mapp[r][c] == ani[0] || mapp[r][c] == '#') {
if (mapp[rr][cc] == ani[0] || mapp[r][c] == ani[0]) flag0 = true;
if (mapp[rr][cc] == ani[1]) flag1 = true;
q.push_back({rr, cc});
vis[rr][cc] = vid;
}
if (mapp[r][c] == ani[1]) {
if (mapp[rr][cc] == ani[1] || mapp[rr][cc] == '#') {
q.push_back({rr, cc});
vis[rr][cc] = vid;
}
}
}
mapp[r][c] = '#';
}
if (not flag0) break;
count += 1;
if (not flag1) break;
count += 1;
vid++;
}
cout << count << '\n';
}
