#include <bits/stdc++.h>
using namespace std;
#define F first
#define S second
#define pb push_back
#define all(a) a.begin(), a.end()
typedef long long ll;
typedef pair<int, int> ii;
void print() {cerr << '\n';} template <typename T1, typename... T2>
void print(const T1 &a, const T2 &...b) { cerr << a << ' ', print(b...); }
const int N = 3000 + 5;
const int mod = 1e9 + 7;
char a[N][N];
int n, m;
namespace sub12
{
class matching
{
private:
int n, t;
vector<vector<int>> a;
vector<int> vis, assigned;
public:
matching(int n)
{
t = 0;
this -> n = n;
a.resize(n + 1);
vis.resize(n + 1);
assigned.resize(n + 1);
}
void add(int u, int v)
{
a[u].pb(v);
}
bool visit(int u)
{
if (vis[u] != t) vis[u] = t;
else return 0;
for (int &v : a[u]) if (!assigned[v] || visit(assigned[v]))
{
assigned[v] = u;
return 1;
}
return 0;
}
int match()
{
int res = 0;
for(int i(0); i <= n; i++)
{
t++;
res += visit(i);
}
return res;
}
};
void solve()
{
vector<ii> s, t;
for (int i = 0; i < n; i++)
for (int j = 0; j + 2 < m; j++)
{
if (a[i][j] == 'R' && a[i][j + 1] == 'G' && a[i][j + 2] == 'W')
s.pb({i, j});
//print(i, j);
}
for (int j = 0; j < m; j++)
for (int i = 0; i + 2 < n; i++)
{
if (a[i][j] == 'R' && a[i + 1][j] == 'G' && a[i + 2][j] == 'W')
t.pb({i, j});
//print(i, j);
}
matching graph(s.size() + t.size());
for (int i = 0; i < (int)s.size(); i++)
for (int j = 0; j < (int)t.size(); j++)
{
bool ok = 0;
for (int x = t[j].F; x <= t[j].F + 2; x++)
for (int y = s[i].S; y <= s[i].S + 2; y++)
if (s[i].F == x && t[j].S == y) ok = 1;
if (ok) graph.add(i, j);
}
cout << s.size() + t.size() - graph.match();
}
}
void solve()
{
cin >> n >> m;
for (int i = 0; i < n; i++)
for (int j = 0; j < m; j++)
cin >> a[i][j];
sub12::solve();
}
signed main()
{
cin.tie(0)->sync_with_stdio(0);
int t = 1;
// cin >> t;
while(t--) solve();
return 0;
}
