#include<bits/stdc++.h>
using namespace std;
int n,m;
char a[1010][1010];
bool f[1010][1010];
void solve(){
	cin>>n>>m;
	for (int i=1;i<=n;i++)
	for (int j=1;j<=m;j++)
	cin>>a[i][j];
	if(a[1][1]=='B'||a[n][m]=='B')
	return cout<<"L"<<"\n",void();
	f[1][1]=1;
	for (int i=1;i<=n;i++)
	for (int j=1;j<=m;j++)
	if((i!=1||j!=1)&&a[i][j]=='W')
	f[i][j]=f[i-1][j]|f[i][j-1];
	else if(a[i][j]=='B')f[i][j]=0;
	if(f[n][m]==0)return cout<<"L"<<"\n",void();
	int ct=0;
	for (int i=1;i<=n;i++)
	for (int j=1;j<=m;j++)
	ct+=(a[i][j]=='W');
	ct-=(n+m-1);
	if(ct&1)cout<<"I\n";
	else cout<<"J\n";
}
int main(){
	ios::sync_with_stdio(0);
	cin.tie(0);cout.tie(0);
	int T;cin>>T;
	while(T--)solve();
}