#include <bits/stdc++.h>
using namespace std;
int dx[4] = {0, 0, 1, -1};
int dy[4] = {1, -1, 0, 0};
int solve(vector<vector<char>>& grid, char cur){
int n = grid.size();
int m = grid[0].size();
deque<vector<int>> dq;
vector<vector<int>> d(n, vector<int>(m, n * m + 1));
if(grid[0][0] == cur){
dq.push_front({0, 0, 0, cur - 'A'});
d[0][0] = 0;
} else {
dq.push_back({0, 0, 1, grid[0][0] - 'A'});
d[0][0] = 1;
}
while(!dq.empty()){
vector<int> curr = dq.front();
dq.pop_front();
for(int i = 0; i < 4; i++){
int X = curr[0] + dx[i];
int Y = curr[1] + dy[i];
if(X >= n || X < 0 || Y >= m || Y < 0) continue;
int cost = 0;
if(grid[X][Y] != curr[3]){
cost = 1;
}
if(cost + d[curr[0]][curr[1]] < d[X][Y]){
d[X][Y] = cost + d[curr[0]][curr[1]];
if(cost == 0) dq.push_front({X, Y, d[X][Y], curr[3]});
else dq.push_back({X, Y, d[X][Y], grid[X][Y]});
}
}
}
return d[n - 1][m - 1];
}
int main(){
int n, m;
cin >> n >> m;
vector<vector<char>> grid(n, vector<char>(m));
bool r = 0;
bool f = 0;
for(int i = 0; i < n; i++){
for(int j = 0; j < m; j++){
cin >> grid[i][j];
if(grid[i][j] == 'F') f = 1;
if(grid[i][j] == 'R') r = 1;
}
}
if(r == 0 || f == 0){
cout << 1 << "\n";
return 0;
}
cout << max(solve(grid, 'F'), solve(grid, 'R')) << "\n";
}
