#include <bits/stdc++.h>
using namespace std;
#define Q (t%2==1 ? q1 : q2)
#define G (t%2==0 ? q1 : q2)
int main() {
cin.tie(0)->sync_with_stdio(0);
int h, w; cin >> h >> w;
vector<vector<int>> grid(h, vector<int>(w, 0));
for (int i = 0; i < h; i++) {
for (int j = 0; j < w; j++) {
char x; cin >> x;
if (x == 'R') grid[i][j] = 1;
else if (x == 'F') grid[i][j] = 2;
}
}
auto coord = [&](int x, int y) {
return w*x + y;
};
auto pc = [&](int c) {
return make_pair(c/w, c%w);
};
auto adj = [&](int c) {
vector<int> r;
auto k = pc(c);
for (int dx = k.first-1; dx <= k.first+1; dx++) {
for (int dy = k.second-1; dy <= k.second+1; dy++) {
if (dx == k.first && dy == k.second) continue;
if (dx != k.first && dy != k.second) continue;
if (dx < 0 || dx >= h || dy < 0 || dy >= w) continue;
r.push_back(coord(dx, dy));
}
}
return r;
};
int t = 0, p = grid[0][0];
vector<int> seen(h*w, 0);
queue<int> q1, q2; q1.push(0); seen[0]++;
while (!(q1.empty() && q2.empty())) {
t++;
while (!Q.empty()) {
int u = Q.front(); Q.pop();
for (auto v : adj(u)) {
if (seen[v]) continue;
int typ = grid[pc(v).first][pc(v).second];
if (typ == 0) continue;
else if (typ == p) Q.push(v);
else G.push(v);
seen[v]++;
}
}
p = 3 - p;
}
cout << t << "\n";
return 0;
}
