#include <cstring>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;

const int N = 105, M = 1 << 10;

int n, m;
char k;
int g[N], cnt[M], f[2][M][M];
vector<int> state;

bool check(int st)
{
    if (st & (st << 1)) return false;
    if (st & (st << 2)) return false;
    return true;
}

int count(int st)
{
    int res = 0;
    for (int i = 0; i < m; i ++)
        res += (st >> i) & 1;
    return res;
}

int main()
{
    cin >> n >> m;
    for (int i = 1; i <= n; i ++)
        for (int j = 0; j < m; j ++)
            cin >> k, g[i] |= (k == 'H') << j;

    for (int i = 0; i < 1 << m; i ++)
        if (check(i))
        {
            state.push_back(i);
            cnt[i] = count(i);
        }

    for (int i = 1; i <= n + 2; i ++)
        for (auto a : state)
            for (auto b : state)
                for (auto c : state)
                {
                    if ((a & b) || (b & c) || (a & c)) continue;
                    if ((g[i] & a) || (g[i - 1] & b)) continue;
                    f[i&1][a][b] = max(f[i&1][a][b], f[(i - 1)&1][b][c] + cnt[a]);
                }
    cout << f[(n + 2)&1][0][0] << endl;
    return 0;
}