#include <iostream>
#include <vector>
#include <string>
#include <queue>
using namespace std;
vector <string> grid;
int n, m;
int dx[] = {-1, 0, 1, 0};
int dy[] = {0, 1, 0, -1};
int bfs() {
int covered = 1;
queue <pair <int, int>> q;
q.push({n-1, m-1});
vector <vector <bool>> vis(n, vector <bool> (m));
vis[n-1][m-1] = true;
char og = grid[n-1][m-1];
if (og == 'R')
grid[n-1][m-1] = 'F';
else
grid[n-1][m-1] = 'R';
while (!q.empty()) {
int x = q.front().first, y = q.front().second;
q.pop();
for (int i = 0; i < 4; i++) {
int nx = x + dx[i];
int ny = y + dy[i];
if (nx < 0 || nx >= n || ny < 0 || ny >= m)
continue;
if (vis[nx][ny] || grid[nx][ny] != og)
continue;
covered++;
if (og == 'R')
grid[nx][ny] = 'F';
else
grid[nx][ny] = 'R';
q.push({nx, ny});
}
}
return covered;
}
int main() {
cin >> n >> m;
grid.resize(n);
for (int i = 0; i < n; i++)
cin >> grid[i];
int ans = 1;
int lst = bfs();
while (true) {
int res = bfs();
ans++;
if (res == lst)
break;
lst = res;
}
cout << ans-1 << '\n';
}
