#include <bits/stdc++.h>
using namespace std;
#define endl "\n"
void solve() {
int n, m;
cin >> n >> m;
vector<string> ve(n);
for (int i = 0; i < n; i++) {
cin >> ve[i];
}
for (int i = 0; i < n; i++) {
for (int j = 0; j < m; j++) {
if(ve[i][j] == 'R') {
ve[i][j] = '0';
} else if(ve[i][j] == 'F'){
ve[i][j] = '1';
}
}
}
vector<queue<array<int, 2>>> que(2);
bool who = ve[n - 1][m - 1] - '0';
que[who].push({n - 1, m - 1});
int cnt = 0;
while(!que[0].empty() || !que[1].empty()) {
while(!que[who].empty()) {
auto [x, y] = que[who].front();
que[who].pop();
if(x != 0) { // TOP
if(ve[x - 1][y] != '.') {
que[ve[x - 1][y] - '0'].push({x - 1, y});
ve[x - 1][y] = '.';
}
}
if(y != m - 1) { // RIGHT
if(ve[x][y + 1] != '.') {
que[ve[x][y + 1] - '0'].push({x, y + 1});
ve[x][y + 1] = '.';
}
}
if(x != n - 1) { // BOT
if(ve[x + 1][y] != '.') {
que[ve[x + 1][y] - '0'].push({x + 1, y});
ve[x + 1][y] = '.';
}
}
if(y != 0) { // LEFT
if(ve[x][y - 1] != '.') {
que[ve[x][y - 1] - '0'].push({x, y - 1});
ve[x][y - 1] = '.';
}
}
}
cnt++;
who = !who;
}
cout << cnt;
}
void init() {}
int32_t main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr), cout.tie(nullptr);
init();
int t = 1;
// cin >> t;
while (t--) {
solve();
cout << endl;
cout.flush();
}
return 0;
}
