#include <bits/stdc++.h>
#pragma GCC optimize("Ofast,unroll-loops")
#define bupol __builtin_popcount
//#define int long long
#define ll long long
#define ld long double
#define fi first
#define se second
#define pb push_back
#define lf (id<<1)
#define rg ((id<<1)|1)
#define md ((l+r)>>1)
using namespace std;
const int MAXN = 2e5+5;
const int MAXK = 205;
const int LOG = 20;
const int MOD = 1e9+7;
const int SQRT = 520;
const int INF = 1e9+10;
typedef pair<int,int> pii;
typedef pair<int,pii> ipii;
vector <int> dx = {-1, 0, 0, 1};
vector <int> dy = {0, -1, 1, 0};
int h, w;
string s[4010];
int vis[4010][4010];
int ans, cnt, tot;
queue <pii> q[3]; // 'R', 'H'
char fnd;
void bfs(int ty){
while(!q[ty].empty()){
int x = q[ty].front().fi, y = q[ty].front().se;
cnt++;
//cout << x << ' ' << y << ' ' << ty << " p\n";
q[ty].pop();
for(int i=0; i<4; i++){
int nx = x+dx[i], ny = y+dy[i];
if(vis[nx][ny] || s[nx][ny] == '.') continue;
vis[nx][ny] = 1;
if(s[nx][ny] == 'R') q[1].push({nx, ny});
else q[2].push({nx, ny});
}
}
}
signed main(){
//ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
cin >> h >> w;
for(int i=1; i<=h; i++){
cin >> s[i];
s[i] = '.'+s[i]+'.';
for(int j=1; j<=w; j++)
if(s[i][j]!='.') tot++;
}
//cout << tot << " t\n";
for(int i=0; i<=w+1; i++){
s[0] += '.'; s[h+1] += '.';
}
fnd = s[1][1]; vis[1][1] = 1; int te = 0;
//cout << fnd << " f\n";
if(fnd=='R'){
q[1].push({1, 1}); te = 1;
} else {
q[2].push({1, 1}); te = 2;
}
cnt = 0;
while(cnt != tot){
ans++;
bfs(te);
// if(fnd='F'){
// for(auto in : vec) cout << in.fi << ' '<< in.se << " p\n";
// exit(0);
// }
if(fnd=='R') fnd = 'H';
else fnd = 'R';
te = 3-te;
//cout << cnt << ' ' << tot << " te\n";
}
cout << ans << '\n';
}
