#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int N = 1005;
const int MOD = 1e9 + 7;
const ll oo = 1e18;
#define fi first
#define se second
#define pb push_back
char a[N][N];
int vs[N][N];
int n, m;
int dx[] = {1, 0, 0, -1};
int dy[] = {0, 1, -1, 0};
int c[256];
int cur, ans;
void inp(void) {
ios::sync_with_stdio(false);
cin.tie(nullptr);
cin >> n >> m;
for (int i = 1; i <= n; i++)
for (int j = 1; j <= m; j++)
cin >> a[i][j];
}
void process(void) {
c['T'] = 0;
c['B'] = 1;
cur = c[a[1][1]];
queue<pair<int,int>> q, nq;
vs[1][1] = 1;
q.push({1,1});
ans = 0;
while (!q.empty()) {
ans++;
while (!q.empty()) {
auto [x,y] = q.front();
q.pop();
for (int d = 0; d < 4; d++) {
int nx = x + dx[d], ny = y + dy[d];
if (nx < 1 || nx > n || ny < 1 || ny > m) continue;
if (vs[nx][ny]) continue;
if (a[nx][ny] != 'B' && a[nx][ny] != 'T') continue;
vs[nx][ny] = 1;
if (c[a[nx][ny]] == cur) q.push({nx, ny});
else nq.push({nx, ny});
}
}
cur = !cur;
q = nq;
while (!nq.empty()) nq.pop();
}
cout << ans;
}
int main(void) {
ios_base::sync_with_stdio(0);
cin.tie(nullptr); cout.tie(nullptr);
inp();
process();
return 0;
}
