#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using ull = unsigned long long;
const bool typetest = 0;
const int N = 3e3 + 5;
struct HopCroft_Karp
{
const int NoMatch = -1;
const int Inf = 1e9 + 7;
int nx, ny;
bool found;
vector<int> match, S, h;
vector<vector<int>> adj;
HopCroft_Karp(int nx, int ny)
{
this->nx = nx;
this->ny = ny;
adj.resize(nx + 1);
match.resize(ny + 1, NoMatch);
h.resize(ny + 1, Inf);
S.reserve(nx);
for (int i = 1; i <= nx; ++i)
S.push_back(i);
}
void AddEdge(int x, int y)
{
adj[x].push_back(y);
}
bool BFS()
{
queue<int> q;
fill(h.begin(), h.end(), 0);
for (auto i : S)
for (auto j : adj[i])
if (h[j] == 0)
{
h[j] = 1;
q.push(j);
}
while (q.size())
{
int c = q.front();
q.pop();
int x;
if ((x = match[c]) == NoMatch)
return true;
for (auto i : adj[x])
if (h[i] == 0)
{
h[i] = h[c] + 1;
q.push(i);
}
}
return false;
}
void dfs(int x, int lv)
{
for (auto i : adj[x])
if (h[i] == lv + 1)
{
if (match[i] != -1)
dfs(match[i], lv + 1);
else
found = 1;
if (found)
{
match[i] = x;
return;
}
}
}
int MaxMatch()
{
int ans(0);
while (BFS())
{
for (int i = S.size() - 1; ~i; --i)
{
found = 0;
dfs(S[i], 0);
if (found)
{
S[i] = S.back();
S.pop_back();
++ans;
}
}
}
return ans;
}
};
const ll Inf = 1e17;
int n, m, nx, ny;
int row[N][N], col[N][N];
string s[N];
void Read()
{
cin >> m >> n;
for (int i = 1; i <= m; ++i)
{
cin >> s[i];
s[i] = " " + s[i];
}
}
void Solve()
{
memset(row, -1, sizeof row);
memset(col, -1, sizeof col);
for (int i = 1; i <= m; ++i)
for (int j = 1; j <= n - 2; ++j)
if (s[i][j] == 'R' && s[i][j + 1] == 'G' && s[i][j + 2] == 'W')
row[i][j] = ++nx;
for (int i = 1; i <= m - 2; ++i)
for (int j = 1; j <= n; ++j)
if (s[i][j] == 'R' && s[i + 1][j] == 'G' && s[i + 2][j] == 'W')
col[i][j] = ++ny;
HopCroft_Karp match(nx, ny);
for (int i = 1; i <= m; ++i)
for (int j = 1; j <= n; ++j)
if (row[i][j] != -1)
{
if (col[i][j] != -1)
match.AddEdge(row[i][j], col[i][j]);
if (i > 1 && col[i - 1][j + 1] != -1)
match.AddEdge(row[i][j], col[i - 1][j + 1]);
if (i > 2 && col[i - 2][j + 2] != -1)
match.AddEdge(row[i][j], col[i - 2][j + 2]);
}
cout << (nx + ny - match.MaxMatch());
}
int32_t main()
{
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int t(1);
if (typetest)
cin >> t;
for (int _ = 1; _ <= t; ++_)
{
Read();
Solve();
}
}
