#include<iostream>
#include<algorithm>
#include<vector>
#include<queue>
using namespace std;
typedef long long ll;
const int N = 3003, N2 = N * N, inf = 1e9 + 7;
int m, n;
char c[N][N];
vector<int> vertexX;
int cnt, num[2][2][N];
int g[N2][3], sz[N2];
void init_graph() {
for (int i = 1, tmp; i <= m; ++i) {
for (int j = 1; j <= n; ++j) if (c[i][j] == 'G') {
// check ngang
if (c[i][j - 1] == 'R' && c[i][j + 1] == 'W') {
num[0][1][j] = ++cnt;
vertexX.push_back(cnt);
tmp = num[1][0][j + 1];
if (tmp)
g[cnt][sz[cnt]++] = tmp;
}
// check dọc
if (c[i - 1][j] == 'R' && c[i + 1][j] == 'W') {
num[1][1][j] = ++cnt;
tmp = num[0][0][j + 1];
if (tmp)
g[tmp][sz[tmp]++] = cnt;
}
if (num[0][1][j] && num[1][1][j])
g[cnt - 1][sz[cnt - 1]++] = cnt;
}
copy(num[0][1] + 1, num[0][1] + n + 1, num[0][0] + 1);
fill(num[0][1] + 1, num[0][1] + n + 1, 0);
copy(num[1][1] + 1, num[1][1] + n + 1, num[1][0] + 1);
fill(num[1][1] + 1, num[1][1] + n + 1, 0);
}
}
int mat[N2], dist[N2];
bool bfs() {
queue<int> q;
dist[0] = inf;
for (int i : vertexX)
if (mat[i]) dist[i] = inf;
else {
dist[i] = 0;
q.push(i);
}
while (!q.empty()) {
int u = q.front(); q.pop();
for (int i = 0, v; i < sz[u]; ++i) {
v = g[u][i];
if (dist[mat[v]] == inf) {
dist[mat[v]] = dist[u] + 1;
q.push(mat[v]);
}
}
}
return dist[0] != inf;
}
bool dfs(int u) {
for (int i = 0, v; i < sz[u]; ++i) {
v = g[u][i];
if (!mat[v] || (dist[mat[v]] == dist[u] + 1 && dfs(mat[v]))) {
mat[v] = u, mat[u] = v;
dist[u] = inf;
return true;
}
}
dist[u] = inf;
return false;
}
int hopcroft_karp() {
int ans(0);
while (bfs()) {
for (int i : vertexX)
if (!mat[i] && dfs(i)) ++ans;
}
return ans;
}
int main() {
cin.tie(NULL)->sync_with_stdio(false);
cin >> m >> n;
for (int i = 1; i <= m; ++i) cin >> (c[i] + 1);
init_graph();
cout << cnt - hopcroft_karp() << '\n';
}
/** /\_/\
* (= ._.)
* / >0 \>1
**/
