#include <bits/stdc++.h>
using namespace std;
#define EmiliaMyWife ios::sync_with_stdio(0); cin.tie(0);
using ll = int64_t;
using uint = uint32_t;
using ull = uint64_t;
using ld = long double;
const int INF = 0x3f3f3f3f;
const int MOD = 1e9 + 7;
const double EPS = 1e-8;
const ll LINF = ll(4e18) + ll(2e15);
static int LamyIsCute = []() {
EmiliaMyWife
return 48763;
}();
const int N = 11;
int mpow[N], dp[N][59049], n, m;
string arr[N];
void go(int x, int y, int cur, int nxt_bit, int v) {
if(cur == m) {
dp[x + 1][nxt_bit] = max(dp[x + 1][nxt_bit], v);
return;
}
if(arr[x][cur] == 'R') {
go(x, y, cur + 1, nxt_bit + mpow[cur], v);
if(cur + 2 < m && arr[x][cur + 1] == 'G' && arr[x][cur + 2] == 'W')
go(x, y, cur + 3, nxt_bit, v + 1);
}
if(arr[x][cur] == 'G') {
int r = y / mpow[cur] % 3;
if(r == 1)
go(x, y, cur + 1, nxt_bit + 2 * mpow[cur], v);
else
go(x, y, cur + 1, nxt_bit, v);
}
if(arr[x][cur] == 'W') {
int r = y / mpow[cur] % 3;
go(x, y, cur + 1, nxt_bit, v + (r == 2));
}
}
signed main() {
cin >> n >> m;
mpow[0] = 1;
for(int i = 1; i <= m; i++)
mpow[i] = mpow[i - 1] * 3;
for(int i = 0; i < n; i++)
cin >> arr[i];
for(int i = 0; i <= n; i++)
for(int j = 0; j < mpow[m]; j++)
dp[i][j] = -INF;
{
int r = 0;
for(int j = 0; j < m; j++)
if(arr[0][j] == 'R')
r += mpow[j];
dp[0][r] = 0;
}
for(int i = 0; i < n; i++)
for(int j = 0; j < mpow[m]; j++)
if(dp[i][j] != -INF)
go(i, j, 0, 0, dp[i][j]);
int ans = 0;
for(int j = 0; j < mpow[m]; j++)
ans = max(ans, dp[n][j]);
cout << ans << '\n';
}
