#include<bits/stdc++.h>
using namespace std;
vector<pair<int, int>> moves={{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
int main() {
cin.tie(0)->sync_with_stdio(false);
int h, w;
cin >> h >> w;
vector<string> tr(h);
for (int i = 0; i < h; i++) {
cin >> tr[i];
}
int ans=0;
char c=tr[0][0];
queue<pair<int, int>> a, b;
a.push({0, 0});
while (!a.empty()) {
auto [x, y]=a.front();
a.pop();
for (auto [dx, dy] : moves) {
if (x+dx<0 || x+dx>=h || y+dy<0 || y+dy>=w) continue;
if (tr[x+dx][y+dy]==c) a.push({x+dx, y+dy});
else if (tr[x+dx][y+dy]!='.') b.push({x+dx, y+dy});
if (tr[x+dx][y+dy]!='.') tr[x+dx][y+dy]='.';
}
if (a.empty()) {
swap(a, b);
ans++;
c='F'+'R'-c;
}
} cout << ans << '\n';
return 0;
}
