#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
int32_t main () {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int N, M;
cin >> N >> M;
vector<vector<int>> arr(N, vector<int>(M));
map<char, int> val;
val['.'] = 1;
val['F'] = 2;
val['R'] = 3;
for (int i = 0;i < N;i ++) {
string S;
cin >> S;
for (int j = 0;j < M;j ++) {
arr[i][j] = val[S[j]];
}
}
assert (arr[0][0] == arr[N - 1][M - 1] && arr[0][0] > 1);
// for (int i = 0;i < N;i ++) {
// for (int j = 0;j < M;j ++) {
// cout << arr[i][j] << " ";
// } cout << "\n";
// } cout << "\n";
vector<int> X = {1, -1, 0, 0};
vector<int> Y = {0, 0, 1, -1};
vector<vector<int>> used(N, vector<int>(M, 0)), submx(N, vector<int>(M, 0));
auto check = [&](int x, int y) -> bool {
if (x < 0 || x >= N || y < 0 || y >= M || used[x][y] == 1 || arr[x][y] <= 1) return 0;
return 1;
};
// for (int i = 0;i < N;i ++) {
// for (int j = 0;j < M;j ++) {
// for (int t = 0;t < 4;t ++) if (check (i + X[t], j + Y[t])) {
// if (arr[i][j] == arr[i + X[t]][j + Y[t]]) {
// DS.add ({i, j}, {i + X[t], j + Y[t]});
// }
// }
// }
// }
// for (int i = 0;i < N;i ++) for (int j = 0;j < M;j ++) used[i][j] = 0;
queue<array<int, 2>> q;
int typ = -1;
function<void(int, int)> dfs_init = [&](int sx, int sy) -> void {
used[sx][sy] = 1;
for(int i = 0 ; i < 4;i++){
int tx = X[i] + sx, ty = Y[i] + sy;
if (check (tx, ty) == true) {
if (arr[tx][ty] == typ) {
dfs_init (tx, ty);
} else {
q.push({tx, ty});
}
}
}
};
q.push({0, 0});
int ans = 0;
while (q.size() > 0) {
auto [sx, sy] = q.front();
q.pop();
if (used[sx][sy] == 1) continue;
// used[sx][sy] = 1;
if (typ != arr[sx][sy]) ans ++;
typ = arr[sx][sy];
dfs_init (sx, sy);
}
cout << ans << "\n";
}
/*
5 6
RRRRRR
.R...R
FRRFRR
FR....
.RRRRR
*/
