#include<bits/stdc++.h>
typedef long long ll;
#define vi vector<int>
#define pb push_back
#define self_min(a, b) a = min(a, b)
#define self_max(a, b) a = max(a, b)
#define V vector
#define yes cout<<"YES\n";
#define no cout<<"NO\n";
#define fs(lcv, hi) for(lcv = 0; lcv < hi; lcv ++)
#define fb(lcv, hi) for(lcv = hi; lcv >= 0; lcv --)
#define loop(lcv, lower, upper) for(lcv = lower; lcv < upper; lcv++)
#define crd(pii) [pii.first][pii.second]
using namespace std;
V<vi> grid;
V<V<V<pair<int, pair<int, int>>>>> adj;
V<V<bool>> vis;
V<V<int>> distances;
int h, w;
void flood_fill(int x, int y);
void process(int x1, int y1, int x2, int y2)
{
if(x1 < 0 || x1 > h - 1 || y1 < 0 || y1 > w-1 || !grid[x1][y1]) return;
if(grid[x1][y1] == grid[x2][y2])
{
adj[x1][y1].pb({0, {x2, y2}});
adj[x2][y2].pb({0, {x1, y1}});
}
else
{
adj[x1][y1].pb({1, {x2, y2}});
adj[x2][y2].pb({1, {x1, y1}});
}
if(!vis[x1][y1])
flood_fill(x1, y1);
}
void flood_fill(int x, int y)
{
vis[x][y] = 1;
process(x - 1, y, x, y);
process(x, y - 1, x, y);
process(x + 1, y, x, y);
process(x, y + 1, x, y);
}
int find_max(int x, int y)
{
deque<pair<int, int>> bfsq;
bfsq.push_back({x, y});
distances[x][y] = 0;
int res = 0;
while(!bfsq.empty())
{
pair<int, int> tp = bfsq.front();
bfsq.pop_front();
// vis[tp.first][tp.second] = 1;
for(auto x : adj crd(tp))
{
if(distances crd(x.second) > distances crd(tp) + x.first)
{
distances crd(x.second) = distances crd(tp) + x.first;
if(x.first) bfsq.push_back(x.second);
else bfsq.push_front(x.second);
self_max(res, distances crd(x.second));
// vis crd(x.second) = 1;
}
}
}
return res;
}
void solve()
{
int i, j;
cin >> h >> w;
grid.assign(h, vi(w, 0));
vis.assign(h, V<bool> (w, 0));
adj.assign(h, V<V<pair<int, pair<int, int>>>>(w));
fs(i, h)
{
string row;
cin >> row;
fs(j, w)
{
if(row[j] == 'F') grid[i][j] = 1;
else if(row[j] == 'R') grid[i][j] = 2;
}
}
flood_fill(0, 0);
distances.assign(h, vi(w, (int)1e9));
cout << 1 + find_max(0, 0) << "\n";
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
solve();
return 0;
}
