/*input
5 8
FFR.....
.FRRR...
.FFFFF..
..RRRFFR
.....FFF
*/
#pragma comment(linker, "/stack:200000000")
#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 ll int
#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 double PI = 3.14159265358979323846264338;
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];
int lev[N][N];
int n,m;
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));
}
queue<pair<pair<int,int>,ll > > q;
stack<pair<pair<int,int>,int> > st;
void dfs(){
}
void solve(){
cin >> n >> m;
RE(i,n){
RE(j,m){
char o;cin >> o;
//cout << o;
if(o == '.')continue;
if(o == 'F')a[i][j] = 1;
else a[i][j] = 2;
}
}
q.push({{1,1},1});
ll ans = 1;
while(!q.empty()){
int i1 = q.front().f.f;
int j1 = q.front().f.s;
ll npara = q.front().s;
q.pop();
if(lev[i1][j1])continue;
ans = max(ans,npara);
st.push({{i1,j1},npara});
while(!st.empty()){
int i = st.top().f.f;
int j = st.top().f.s;
int para = st.top().s;
lev[i][j] = para;
st.pop();
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]){
if(a[ni][nj] and !lev[ni][nj])q.push({{ni,nj},para+1});
continue;
}
if(!lev[ni][nj])st.push({{ni,nj},para});
}
}
}
cout << ans;
}
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;
}
