#include <bits/stdc++.h>
using namespace std;
const int dx[4] = {-1, 0, 1, 0};
const int dy[4] = {0, 1, 0, -1};
const int MAXN = 4000 + 5;
char ch;
int n, m, ans;
int g[MAXN][MAXN];
bool seen[MAXN][MAXN];
queue<pair<int, int>> qq;
int main()
{
cin >> n >> m;
for (int i = 1; i <= n; i++)
{
ch = getchar();
for (int j = 1; j <= m; j++)
{
ch = getchar();
switch (ch)
{
case 'R':
g[i][j] = 0;
break;
case '.':
g[i][j] = -1;
break;
case 'F':
g[i][j] = 1;
break;
}
}
}
while (true)
{
for (int i = 0; i <= n + 1; i++)
for (int j = 0; j <= m + 1; j++)
seen[i][j] = false;
ans++;
qq.push(make_pair(1, 1));
while (!qq.empty())
{
pair<int, int> now = qq.front();
qq.pop();
int x = now.first, y = now.second;
seen[x][y] = true;
for (int i = 0; i < 4; i++)
{
int fx = x + dx[i], fy = y + dy[i];
if (fx < 1 || fy < 1 || fx > n || fy > m || g[x][y] != g[fx][fy] || seen[fx][fy])
continue;
qq.push(make_pair(fx, fy));
}
}
for (int i = 1; i <= n; i++)
for (int j = 1; j <= m; j++)
if (seen[i][j])
g[i][j] = 1 - g[i][j];
bool ra = false, fo = false;
for (int i = 1; i <= n; i++)
for (int j = 1; j <= m; j++)
{
if (g[i][j] == 0)
ra = true;
else if (g[i][j] == 1)
fo = true;
}
if (!(ra && fo))
break;
}
cout << ans + 1 << endl;
return 0;
}
