和《算法进阶》上面的单调栈基本一样，因为都是矩形，我们对于当前这一行，假设矩形的底已经固定，就然后跑一遍书上的单调栈就可以了。

#include <cstdio>
#include <cstring>
#include <iostream>
using namespace std;
const int N = 1006;
int n, m, a[N][N], p, s[N], w[N];
int main() {
    scanf("%d%d", &n, &m);
    char ss[2];
    for (int i = 1; i <= n; i++)
    for (int j = 1; j <= m; j++) {
        scanf("%s", ss);
        if (ss[0] == 'F') a[i][j] = a[i-1][j] + 1;
        else a[i][j] = 0;
    }
    int ans = 0;
    for (int i = 1; i <= n; i++) {
        a[i][m+1] = p = 0;
        for (int j = 1; j <= m + 1; j++) {
            if (a[i][j] > s[p]) {
                s[++p] = a[i][j], w[p] = 1;
            }
            else {
                int width = 0;
                while (s[p] > a[i][j]) {
                    width += w[p];
                    ans = max(ans, width * s[p]);
                    p--;
                }
                s[++p] = a[i][j], w[p] = width + 1;
            }
        }
    }
    printf("%d\n", 3 * ans);
    return 0;
}