#include <iostream>
#include <vector>
#include <deque>
using namespace std;
#define AT(grid, r, c) (grid[(r) * W + (c)])
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int H, W;
cin >> H >> W;
vector<char> mapp(H * W);
for (int i = 0; i < H; ++i) {
string line;
cin >> line;
for (int j = 0; j < W; ++j) {
AT(mapp, i, j) = line[j];
}
}
char first = (AT(mapp, 0, 0) == 'R') ? 'R' : 'F';
char second = (first == 'R') ? 'F' : 'R';
vector<char> ani = {first, second};
int dirs[4][2] = { {0,1}, {1,0}, {0,-1}, {-1,0} };
vector<int> vis(H * W, 0);
int vid = 1;
int count = 0;
while (true) {
bool flag0 = false, flag1 = false;
deque<pair<int, int>> q;
q.push_back({0, 0});
AT(vis, 0, 0) = vid;
while (!q.empty()) {
auto [r, c] = q.front();
q.pop_front();
char current = AT(mapp, r, c);
for (int d = 0; d < 4; ++d) {
int rr = r + dirs[d][0];
int cc = c + dirs[d][1];
if (rr < 0 || rr >= H || cc < 0 || cc >= W) continue;
int idx = rr * W + cc;
if (vis[idx] == vid) continue;
char next = AT(mapp, rr, cc);
if (next == '.') continue;
if (current == ani[0] || current == '#') {
vis[idx] = vid;
if (next == ani[0] || current == ani[0]) flag0 = true;
if (next == ani[1]) flag1 = true;
q.push_back({rr, cc});
}
if (current == ani[1]) {
if (next == ani[1] || next == '#') {
vis[idx] = vid;
q.push_back({rr, cc});
}
}
}
AT(mapp, r, c) = '#';
}
if (!flag0) break;
count += 1;
if (!flag1) break;
count += 1;
vid++;
}
cout << count << '\n';
return 0;
}
