/*
ID: varunra2
LANG: C++
TASK: tracks
*/
#include <bits/stdc++.h>
using namespace std;
#ifdef DEBUG
#include "lib/debug.h"
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#define debug_arr(...) \
cerr << "[" << #__VA_ARGS__ << "]:", debug_arr(__VA_ARGS__)
#pragma GCC diagnostic ignored "-Wsign-compare"
//#pragma GCC diagnostic ignored "-Wunused-parameter"
//#pragma GCC diagnostic ignored "-Wunused-variable"
#else
#define debug(...) 42
#endif
#define EPS 1e-9
#define IN(A, B, C) assert(B <= A && A <= C)
#define INF (int)1e9
#define MEM(a, b) memset(a, (b), sizeof(a))
#define MOD 1000000007
#define MP make_pair
#define PB push_back
#define all(cont) cont.begin(), cont.end()
#define rall(cont) cont.end(), cont.begin()
#define x first
#define y second
const double PI = acos(-1.0);
typedef long long ll;
typedef long double ld;
typedef pair<int, int> PII;
typedef map<int, int> MPII;
typedef multiset<int> MSETI;
typedef set<int> SETI;
typedef set<string> SETS;
typedef vector<int> VI;
typedef vector<PII> VII;
typedef vector<VI> VVI;
typedef vector<string> VS;
#define rep(i, a, b) for (int i = a; i < (b); ++i)
#define trav(a, x) for (auto& a : x)
#define sz(x) (int)(x).size()
typedef pair<int, int> pii;
typedef vector<int> vi;
#pragma GCC diagnostic ignored "-Wsign-compare"
// util functions
VVI vals;
int h, w;
vector<vector<bool>> vis;
int get(PII a, PII b) { return vals[a.x][a.y] != vals[b.x][b.y]; }
bool inbnds(PII a) {
bool x = a.x >= 0 and a.x < h and a.y >= 0 and a.y < w;
if (x == false) return false;
return vals[a.x][a.y] != 0 and vis[a.x][a.y] == false;
}
VI dx = {0, -1, 0, 1};
VI dy = {1, 0, -1, 0};
int dij() {
deque<pair<int, PII>> dq;
dq.PB(MP(0, MP(0, 0)));
int ret = 0;
while (!dq.empty()) {
auto x = dq.front();
dq.pop_front();
ret = max(ret, x.x);
if (vis[x.y.x][x.y.y]) continue;
vis[x.y.x][x.y.y] = true;
for (int i = 0; i < 4; i++) {
PII nw = MP(x.y.x + dx[i], x.y.y + dy[i]);
if (inbnds(nw)) {
int gt = get(x.y, nw);
if (gt == 1) {
dq.PB(MP(x.x + gt, nw));
} else
dq.push_front(MP(x.x + gt, nw));
}
}
}
return ret;
}
int main() {
// #ifndef ONLINE_JUDGE
// freopen("tracks.in", "r", stdin);
// freopen("tracks.out", "w", stdout);
// #endif
cin.sync_with_stdio(0);
cin.tie(0);
cin >> h >> w;
vals.resize(h);
vis.resize(h);
for (int i = 0; i < h; i++) {
vals[i].assign(w, 0);
vis[i].assign(w, false);
for (int j = 0; j < w; j++) {
char c;
cin >> c;
if (c == 'R')
vals[i][j] = 1;
else if(c == 'F')
vals[i][j] = 2;
}
}
cout << dij() + 1 << '\n';
return 0;
}
