//#define _GLIBCXX_DEBUG
//#pragma GCC optimize("Ofast")
//#pragma GCC optimize("unroll-loops")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#include <bits/stdc++.h>
using namespace std;
//randoms
//chrono::steady_clock::now().time_since_epoch().count()
mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());
#define ll long long
#define trace(x) cout << #x << " = " << (x) << endl;
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
#define uniq(x) x.resize(unique(all(x)) - begin(x))
#define ld long double
#define sz(s) (int) size(s)
#define pii pair<int, int>
#define mp(x, y) make_pair(x, y)
#define mt make_tuple
#define int128 __int128
template<typename T>
void ckmn(T &x, T y) { if (x > y) { x = y; }}
template<typename T>
void ckmx(T &x, T y) { if (x < y) { x = y; }}
int rand(int l, int r) { return (int) ((ll) rnd() % (r - l + 1)) + l; }
const ll infL = 1e18;
const int infI = 1e9 + 7;
const int N = 3000000;
const ll mod = 998244353;
const ld eps = 1e-9;
int g[N][3];
int used[N], pr[N], T;
bool dfs(int v) {
if (used[v] == T) return false;
used[v] = T;
for (int to : g[v]) {
if (to != -1 && pr[to] == -1) {
pr[to] = v;
return true;
}
}
for (int to : g[v]) {
if (to != -1 && dfs(pr[to])) {
pr[to] = v;
return true;
}
}
return false;
}
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int n, m;
cin >> n >> m;
vector<string> s(n);
vector<vector<int>> R(n, vector<int>(m, -1));
vector<vector<int>> D(n, vector<int>(m, -1));
for (int i = 0; i < n; ++i) {
cin >> s[i];
}
memset(g, -1, sizeof(g));
int last = -1;
for (int i = 1; i < n - 1; ++i) {
for (int j = 0; j < m; ++j) {
if (s[i][j] == 'G' && s[i - 1][j] == 'R' && s[i + 1][j] == 'W') {
D[i][j] = D[i - 1][j] = D[i + 1][j] = ++last;
}
}
}
int gg = last;
last = -1;
for (int i = 0; i < n; ++i) {
for (int j = 1; j < m - 1; ++j) {
if (s[i][j] == 'G' && s[i][j - 1] == 'R' && s[i][j + 1] == 'W') {
R[i][j] = R[i][j - 1] = R[i][j + 1] = ++last;
}
}
}
for (int i = 0; i < n; ++i) {
for (int j = 0; j < m; ++j) {
if (D[i][j] != -1 && R[i][j] != -1) {
g[D[i][j]][used[D[i][j]]++] = R[i][j];
}
}
}
memset(used, 0, sizeof(used));
memset(pr, -1, sizeof(pr));
int ans = 0;
for (int i = 0; i <= gg; ++i) {
++T;
if (dfs(i))
++ans;
}
cout << gg + last - ans + 2;
return 0;
}
