题解（求赞）

#include<bits/stdc++.h>
using namespace std;
#define ll long long
int main(){
    int n,m,ans=0;
    cin>>n>>m;
    vector<vector<char>> maze(n+1,vector<char>(m+1,'R'));
    vector<vector<int>> mnhigh(n+1,vector<int>(m+1,0));
    
    for(int i=1;i<=n;i++){
        for(int j=1;j<=m;j++){
            cin>>maze[i][j];
            if(maze[i-1][j]=='R'){
                mnhigh[i][j]=1;
            }else{
                mnhigh[i][j]=mnhigh[i-1][j]+1;
            }
        }
    }
    for(int i=1;i<=n;i++){
        for(int j=1;j<=m;j++){
            int sum=1,high=mnhigh[i][j];
            if(maze[i][j]=='R'){
                continue;
            } 
            for(int k=j;k>=1;k--){
                if(maze[i][k]=='R') break;
                high=min(high,mnhigh[i][k]);
                sum=max(sum,(j-k+1)*high);
            }
            ans=max(ans,sum);
        }
    }

    cout<<ans*3;
	return 0;
}