/*input
5 8
FFR.....
.FRRR...
.FFFFF..
..RRRFFR
.....FFF
*/
#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
#define double long double
#define f first
#define s second
#define mp make_pair
#define pb push_back
#define RE(i,n) for (int i = 1; i <= n; i++)
#define RED(i,n) for (int i = n; i > 0; i--)
#define REPS(i,n) for(int i = 1; (i*i) <= n; i++)
#define REP(i,n) for (int i = 0; i < (int)n; i++)
#define FOR(i,a,b) for (int i = a; i < b; i++)
#define REPD(i,n) for (int i = n-1; i >= 0; i--)
#define FORD(i,a,b) for (int i = a; i >= b; i--)
#define all(v) v.begin(),v.end()
#define pii pair<int,int>
#define vi vector<int>
#define vvi vector<vi>
#define print(arr) for (auto it = arr.begin(); it != arr.end(); ++it) cout << *it << " "; cout << endl;
#define debug(x) cout << x << endl;
#define debug2(x,y) cout << x << " " << y << endl;
#define debug3(x,y,z) cout << x << " " << y << " " << z << endl;
typedef tree<
int,
null_type,
less<int>,
rb_tree_tag,
tree_order_statistics_node_update>
ordered_set;
const int MOD = 1e9+7;
const double PI = 3.14159265358979323846264338;
int raise(int a,int n,int m = MOD){
if(n == 0)return 1;
if(n == 1)return a;
int x = 1;
x *= raise(a,n/2,m);
x %= m;
x *= x;
x %= m;
if(n%2)x*= a;
x %= m;
return x;
}
int floor1(int n,int k){
if(n%k == 0 || n >= 0)return n/k;
return (n/k)-1;
}
int ceil1(int n,int k){
return floor1(n+k-1,k);
}
const int N = 4001;
int a[N][N];
bool vis[N][N];
int comp[N][N];
int newvis[N*N];
int n,m;
set<int> adj[N*N];
int cur = 1;
pair<int,int> xd[] = {{-1,0},{0,-1},{1,0},{0,1}};
bool ok(int x,int y){
return (x and y and (x <= n) and (y <= m));
}
void dfs(int i,int j){
if(vis[i][j])return;
vis[i][j] = 1;
comp[i][j] = cur;
REP(k,4){
int ni = i+xd[k].f;
int nj = j+xd[k].s;
if(!ok(ni,nj))continue;
if(a[i][j] != a[ni][nj])continue;
dfs(ni,nj);
}
}
int bfs(){
newvis[1] = 1;
queue<int> q;
int ans = 1;
q.push(1);
while(!q.empty()){
int u = q.front();q.pop();
for(int v:adj[u]){
if(newvis[v])continue;
newvis[v] = newvis[u]+1;
ans = max(ans,newvis[v]);
q.push(v);
}
}
return ans;
}
void solve(){
cin >> n >> m;
RE(i,n){
RE(j,m){
char o;cin >> o;
//cout << o;
if(o == '.'){vis[i][j] = 1;comp[i][j] = 0;continue;}
if(o == 'F')a[i][j] = 1;
else a[i][j] = 2;
}
// cout << endl;
}
RE(i,n){
RE(j,m){
if(vis[i][j])continue;
dfs(i,j);
cur++;
}
}
// newvis.resize(cur,-1);
// adj.resize(cur);
RE(i,n){
RE(j,m){
if(!comp[i][j])continue;
REP(k,4){
int ni = i+xd[k].f;
int nj = j+xd[k].s;
if(ok(ni,nj) and comp[ni][nj] and comp[ni][nj] != comp[i][j]){
adj[comp[i][j]].insert(comp[ni][nj]);
}
}
}
}
cout << bfs();
}
signed main(){
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
//freopen(".in","r",stdin);freopen(".out","w",stdout);
int t = 1;
//cin >> t;
while(t--){
solve();
}
return 0;
}
