#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;
getline(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 flag = false;
while(true) {
for (char a : ani) {
flag = false;
vector<vector<bool>> vis(H, vector<bool>(W, false));
vis[0][0] = true;
queue<pair<int, int>> q;
q.push({0,0});
while (!q.empty()) {
int r = q.front().first;
int c = q.front().second;
q.pop();
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]) continue;
if (mapp[rr][cc] == a || mapp[rr][cc] == '#') {
vis[rr][cc] = true;
if (mapp[rr][cc] == a) { flag = true; mapp[rr][cc] = '#'; }
q.push({rr, cc});
}
}
}
if (not flag) break;
count += 1;
}
if (not flag) break;
}
cout << count;
}
