#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int N = 3000 + 24;
int n, m; char a[N][N]; bool ok[N][N][2];
vector<int> g[N * N];
int tdfs = 0; int match[N * N], vis[N * N];
int id(int i, int j) {
return (i - 1) * m + j;
}
bool kuhn(int u) {
if (vis[u] == tdfs) return 0;
vis[u] = tdfs;
for (int v: g[u]) {
if (match[v] == 0 || kuhn(match[v])) {
match[v] = u;
return 1;
}
}
return 0;
}
void solve() {
cin >> n >> m;
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= m; j++) {
cin >> a[i][j];
}
}
int cnt_node = 0;
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= m; j++) {
if (i + 2 <= m && a[i][j] == 'R' && a[i + 1][j] == 'G' && a[i + 2][j] == 'W') {
ok[i][j][0] = 1;
cnt_node++;
}
if (j + 2 <= m && a[i][j] == 'R' && a[i][j + 1] == 'G' && a[i][j + 2] == 'W') {
ok[i][j][1] = 1;
cnt_node++;
}
}
}
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= m; j++) {
if (!ok[i][j][1]) continue;
if (ok[i][j][0]) g[id(i, j)].push_back(id(i, j));
if (i - 1 >= 1 && j - 1 >= 1 && ok[i - 1][j - 1][0]) g[id(i, j)].push_back(id(i - 1, j - 1));
if (i - 2 >= 1 && j - 2 >= 1 && ok[i - 2][j - 2][0]) g[id(i, j)].push_back(id(i - 2, j - 2));
}
}
for (int i = 1; i <= n * m; i++) {
tdfs++;
kuhn(i);
}
int cnt_match = 0;
for (int i = 1; i <= n * m; i++) {
if (match[i] != 0) cnt_match++;
}
cout << cnt_node - cnt_match << '\n';
}
int main() {
cin.tie(0) -> sync_with_stdio(0);
int T = 1; // cin >> T;
while (T--) {
solve();
}
}
