#include <bits/stdc++.h>

using namespace std;
const int N = 110;
const int M = 1 << 10;
int n, m;
int g[N];
int cnt[M];
int f[2][M][M];
vector<int> st;
vector<int> head[M];

bool check(int x) {
    return !(x & x >> 1 || x & x >> 2);
}

int count(int x) {
    int res = 0;
    while (x) {
        x = x & (x - 1);
        res++;
    }
    return res;
}

int main() {
    scanf("%d %d", &n, &m);
    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= m; j++) {
            char c;
            scanf(" %c", &c);
            if (c == 'H') g[i] += 1 << (j - 1);
        }

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

    for (int a : st)
        for (int b : st)
            if (!(a & b))
                head[a].push_back(b);

    for (int i = 1; i <= n; i++)
        for (int a : st) {
            if (g[i] & a) continue;
            for (int b : head[a])
                for (int c : head[b])
                    if (!(a & c))
                        f[i & 1][a][b] = max(f[i & 1][a][b], f[i - 1 & 1][b][c] + cnt[a]);
        }

    int res = 0;
    for (int a : st)
        for (int b : head[a])
            res = max(res, f[n & 1][a][b]);

    printf("%d\n", res);
    return 0;
}