//This code is written by sarthakgangwal
#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace std;
using namespace __gnu_pbds;
template<class T> using oset =tree<T, null_type, less<T>, rb_tree_tag,tree_order_statistics_node_update>;
#define tc int t;cin>>t;while(t--)
#define el "/n"
#define sp ' '
#define fast ios::sync_with_stdio(0); cin.tie(0);
#define ll long long int
#define ld long double
#define vll vector<long long int>
#define vvll vector<vector<long long int>>
#define vvpll vector<vector<pair<long long int, long long int>>>
#define vpll vector<pair<long long int,long long int>>
#define vb vector<bool>
#define pb push_back
#define pll pair<long long int,long long int>
#define ff first
#define ss second
#define I(x) ll x;cin>>x
#define CC(x) cout << (x) << endl
#define mod 1000000007
#define PI 3.14159265
long long INF = 2e18;
#define vll_in(v,n) for(ll i=0;i<=n-1;i++){ ll x;cin>>x; v.push_back(x);}
#define vvll_in(mat,r,c) for(ll i=0;i<=r-1;i++){ vector<ll> v;for(ll j=0;j<=c-1;j++){ll x;cin>>x;v.push_back(x);};mat.push_back(v);}
void print(bool k){cout << (k ? "YES" : "NO") <<"\n";}
void print(vll k,string sep = " ",string endline = "\n") {for (ll &i : k) cout << i << sep; cout << endline;}
#define all(x) (x).begin(), (x).end()
/*-------------------------------------Imp Concepts---------------------------------------------->
48-57 -> 0-9
65-90 -> A-Z
97-122 -> a-z
(a +-* b) mod M = ((a mod M) +-* (b mod M)) mod M.
use ordered set using oset<ll> , 2 extra functions
.order_of_key(k) gives number of items strictly smaller than k
.find_by_order(k) gives iterator to kth element in set 0 indexing
rest all functionalities are same as stl set like lowerbound upperbound erase find etc
use ordered multiset using oset<pll>
search upper_bound({val,-1})
insert insert({val,index}) index used so same val can be inserted uniquely
delete .erase( .upper_bound({val,-1}))
-----------------------------CODE BEGIN :)-----------------------------------------*/
//https://oj.uz/problem/view/BOI13_tracks
int main(){
fast
{
I(h);I(w);
// ll mat[h+2][w+2]={0};
vvll mat(h+2,vll(w+2,0));
for(ll i=1;i<=h;i++){
for(ll j=1;j<=w;j++){
char x;cin>>x;
if(x=='F'){mat[i][j]=1;}
if(x=='R'){mat[i][j]=2;}
}
}
bool vis[h+2][w+2]={0};
ll ans=1;
ll movx[4]={1,0,-1,0}, movy[4]={0,1,0,-1};
priority_queue<pair<ll,pll>, vector<pair<ll,pll>>, greater<pair<ll,pll>>> pq;
pq.push({1,{1,1}}); vis[1][1]=1;
while(!pq.empty()){
pair<ll,pll> T = pq.top(); pq.pop();
ll x=T.ss.ff, y=T.ss.ss, d=T.ff;
// cout<<x<<sp<<y<<sp<<d<<endl;
for(ll i=0;i<4;i++){
ll xx=x+movx[i], yy=y+movy[i];
if(mat[xx][yy]==0){continue;}
else if(vis[xx][yy]==0 && mat[xx][yy]==mat[x][y]){
vis[xx][yy]=1; pq.push({d,{xx,yy}});
}
else if(vis[xx][yy]==0 && mat[xx][yy]!=mat[x][y]){
vis[xx][yy]=1; pq.push({d+1,{xx,yy}});
ans=max(ans,d+1);
}
}
}
CC(ans);
}
}
