```
/*
* Author: Arpit Bhayani
* https://arpitbhayani.me
*/
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <climits>
#include <deque>
#include <iostream>
#include <list>
#include <limits>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <vector>
#define ll long long
#define MIN(a, b) a < b ? a : b
#define MAX(a, b) a > b ? a : b
using namespace std;
int readline(char *str) {
int i = 0;
char ch;
while((ch = getchar()) != '\n') {
str[i++] = ch;
}
str[i] = '\0';
return i;
}
char arr[16][16];
class compar {
public:
bool operator() (int *a, int *b) {
return a[2] < b[2];
}
};
priority_queue< int *, vector<int *>, compar > q;
void make_all(int *plus, char ch) {
for(int i = 0; i < plus[2]; i++) {
arr[plus[0] + i][plus[1]] = ch;
arr[plus[0] - i][plus[1]] = ch;
}
for(int j = 0; j < plus[2]; j++) {
arr[plus[0]][plus[1] + j] = ch;
arr[plus[0]][plus[1] - j] = ch;
}
}
int process(int r, int c) {
int max_area = -1;
for(int i = 0 ; i < r; i++) {
for(int j = 0 ; j < c; j++) {
if(arr[i][j] == 'G') {
int s = 1;
int left = j - 1;
int right = j + 1;
int up = i - 1;
int down = i + 1;
while( left >= 0 && right < c && up >= 0 && down < r ) {
if(arr[i][left] != 'G' || arr[i][right] != 'G' || arr[up][j] != 'G' || arr[down][j] != 'G') {
break;
}
s++;
left--;
right++;
up --;
down++;
}
int *t = (int *) malloc(3 * sizeof(int));
t[0] = i;
t[1] = j;
t[2] = s;
q.push(t);
}
}
}
while(!q.empty()) {
int *first_plus = q.top();
priority_queue< int *, vector<int *>, compar > tq;
make_all(first_plus, 'B');
for(int i = 0 ; i < r; i++) {
for(int j = 0 ; j < c; j++) {
if(arr[i][j] == 'G') {
int s = 1;
int left = j - 1;
int right = j + 1;
int up = i - 1;
int down = i + 1;
while( left >= 0 && right < c && up >= 0 && down < r ) {
if(arr[i][left] != 'G' || arr[i][right] != 'G' || arr[up][j] != 'G' || arr[down][j] != 'G') {
break;
}
s++;
left--;
right++;
up --;
down++;
}
int *t = (int *) malloc(3 * sizeof(int));
t[0] = i;
t[1] = j;
t[2] = s;
tq.push(t);
}
}
}
int * seconds_plus = tq.top();
max_area = MAX(max_area, ( (first_plus[2] - 1)*4 + 1) * ((seconds_plus[2] - 1)*4 + 1) );
make_all(first_plus, 'G');
while(!tq.empty()) {
int *x = tq.top();
free(x);
tq.pop();
}
q.pop();
}
return max_area;
}
int main(int argc, char *argv[]) {
int r, c;
scanf("%d%d", &r, &c);
for(int i = 0 ; i < r; i++) {
scanf("%s", arr[i]);
}
printf("%d\n", process(r, c));
return 0;
}
```

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