#include <bits/stdc++.h>
using namespace std;
#define idata vector<int>
#define imap vector<idata>
#define EMPTY -1
#define FOX 0
#define RABBIT 1
#define di pair<int, int>
imap positions;
int height, width;
imap visited;
int stage = 1;
void try_add (deque<di> &dq, int x, int y, int nx, int ny) {
if (positions[nx][ny] == EMPTY) return ;
if (visited [nx][ny] != EMPTY) return ;
int valuation = positions[nx][ny] == positions[x][y] ? 0 : 1;
visited[nx][ny] = visited[x][y] + valuation;
if (valuation == 0) dq.push_front({ nx, ny });
if (valuation == 1) dq.push_back ({ nx, ny });
}
int bfs () {
deque<di> point_queue;
point_queue.push_front({ 0, 0 });
visited[0][0] = 1;
int max_stage = 0;
while (point_queue.size() != 0) {
di meta = point_queue.front();
point_queue.pop_front();
int x, y; x = meta.first; y = meta.second;
max_stage = max(max_stage, visited[x][y]);
if (x != 0) try_add(point_queue, x, y, x - 1, y);
if (y != 0) try_add(point_queue, x, y, x, y - 1);
if (x != height - 1) try_add(point_queue, x, y, x + 1, y);
if (y != width - 1) try_add(point_queue, x, y, x, y + 1);
}
return max_stage;
}
int main () {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cin >> height >> width;
positions.resize( height, idata(width, EMPTY) );
visited .resize( height, idata(width, EMPTY) );
for (int h = 0; h < height; h ++) {
string buffer;
cin >> buffer;
for (int w = 0; w < width; w ++) {
int mu = EMPTY;
if (buffer[w] == 'F') mu = FOX;
if (buffer[w] == 'R') mu = RABBIT;
positions[h][w] = mu;
}
}
cout << bfs();
}
