每句两个顶点确定正方形，取max即可
#include<iostream>
#include<cstdio>
using namespace std;
int n,x,y,s,ans;
char a[105][105];
int main()
{
scanf("%d\n",&n);
for(int i=1;i<=n;i++)
scanf("%s",a[i]+1);
for(int i=1;i<=n;i++)
for(int j=1;j<=n;j++)
for(int k=i+1;k<=n;k++)
for(int t=1;t<=j;t++)
{
int x=j-t,y=k-i,x3=k+x,y3=t+y,x4=i+x,y4=j+y;
if(x3<1||x3>n||y3<1||y3>n||x4<1||x4>n||y4<1||y4>n)
continue;
s=0;
if(a[i][j]=='B'||a[k][t]=='B'||a[x3][y3]=='B'||a[x4][y4]=='B')
continue;
if(a[i][j]=='J')
s++;
if(a[k][t]=='J')
s++;
if(a[x3][y3]=='J')
s++;
if(a[x4][y4]=='J')
s++;
if(s>=3)
ans=max(ans,x*x+y*y);
}
printf("%d\n",ans);
return 0;
}