#include <iostream>
#include <vector>
#include <string>
#include <queue>
using namespace std;
#define TEST
#define all(x) (x).begin(), (x).end()
const vector<pair<int,int>> DIR = { {1,0 } , {-1,0} , {0,1} ,{0,-1}} ;
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int H, W;
cin >> H >> W;
vector<vector<char>> field( H+1, vector<char>( W+1 ) );
for (int i =1 ; i <= H ; i++) {
string s;
cin >> s;
for (int j =1 ; j <= W ; j++) {
field[i][j] = s[j-1];
}
}
int count{0};
queue<pair<int,int>> q;
queue<pair<int,int>> pending_q;
vector<vector<bool>> vis(H+1, vector<bool>(W+1, false));
char cur_animal = field[1][1];
vis[1][1] = true;
q.push({1,1});
while (!pending_q.empty() || !q.empty()) {
count++;
while (!q.empty()) {
auto [i_u, j_u] = q.front();
q.pop();
for (auto [di ,dj] : DIR) {
int i_v = i_u + di;
int j_v = j_u + dj;
if (i_v < 1 || i_v > H || j_v < 1 || j_v > W) { // out of bounds
continue;
}
if (vis[i_v][j_v]) { continue;} // visited;
vis[i_v][j_v] = true;
if (field[i_v][j_v]== '.') {continue;} //empty square
if ( cur_animal == field[i_v][j_v] ) {
q.push({i_v,j_v});
}else {
pending_q.push({i_v,j_v});
}
}
}
q = pending_q;
pending_q= {};
if (cur_animal == 'R') {
cur_animal = 'F';
}else {
cur_animal = 'R';
}
}
cout << count << endl;
return 0;
}
