#include<bits/stdc++.h>
using namespace std ;
typedef long long ll ;
typedef unsigned long long ull ;
typedef pair < int , int > pii ;
typedef vector < int > vi ;
#define fi first
#define se second
mt19937 rng(chrono::high_resolution_clock::now().time_since_epoch().count());

#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()

const int MAXN = 2e5 + 7 ;

int n , m , k ;
vector < int > v[ 2 ][ MAXN ] ;
vector < int > gr[ MAXN ] ;

int lft[ 2 ][ MAXN ] ;

void dfs ( int x , int hh ) {
    lft[ hh ][ x ] = 0 ;
    if ( v[ hh ][ x ].empty ( ) == true ) {
        lft[ hh ][ x ] = x ;
        k = max ( k , x ) ;
    }
    for ( auto y : v[ hh ][ x ] ) {
        dfs ( y , hh ) ;
        if ( lft[ hh ][ x ] > 0 && lft[ hh ][ y ] > 0 ) {
            gr[ lft[ hh ][ x ] ].push_back ( lft[ hh ][ y ] ) ;
            gr[ lft[ hh ][ y ] ].push_back ( lft[ hh ][ x ] ) ;
            lft[ hh ][ x ] = 0 ;
        }
        else if ( lft[ hh ][ x ] == 0 && lft[ hh ][ y ] > 0 ) {
            lft[ hh ][ x ] = lft[ hh ][ y ] ;
        }
    }
}

int ans[ MAXN ] ;


void mrk ( int x , int prv , int col ) {
    ans[ x ] = col ;
    if ( gr[ x ].empty ( ) == true ) { return ; }
    if ( prv == gr[ x ][ 0 ] ) {
        if ( ans[ gr[ x ][ 1 ] ] == 0 ) { 
            mrk ( gr[ x ][ 1 ] , x , 3 - col ) ;
        }
    }
    else {
        if ( ans[ gr[ x ][ 0 ] ] == 0 ) { 
            mrk ( gr[ x ][ 0 ] , x , 3 - col ) ;
        }
    }
}

void solve ( ) {
    cin >> n >> m ;
    k = 0 ;
    for ( int i = 0 ; i <= max ( n , m ) ; ++ i ) {
        v[ 0 ][ i ].clear ( ) , v[ 1 ][ i ].clear ( ) ;
    }
    for ( int i = 1 , x ; i < n ; ++ i ) {
        cin >> x ;
        v[ 0 ][ x ].push_back ( i ) ;
    }
    for ( int i = 1 , x ; i < m ; ++ i ) {
        cin >> x ;
        v[ 1 ][ x ].push_back ( i ) ;
    }
    for ( int i = 0 ; i <= max ( n , m ) ; ++ i ) {
        gr[ i ].clear ( ) ;
        ans[ i ] = 0 ;
    }

    dfs ( n , 0 ) ;
    dfs ( m , 1 ) ;
    int ori = k ;
    if ( ( k % 2 ) == 1 ) {
        if ( lft[ 0 ][ n ] != lft[ 1 ][ m ] ) {
            gr[ lft[ 0 ][ n ] ].push_back ( lft[ 1 ][ m ] ) ;
            gr[ lft[ 1 ][ m ] ].push_back ( lft[ 0 ][ n ] ) ;
        }
    }
    for ( int i = 1 ; i <= ori ; ++ i ) {
        if ( ans[ i ] == 0 ) {
            mrk ( i , -1 , 1 ) ;
        }
    }
    for ( int i = 1 ; i <= ori ; ++ i ) {
        if ( ans[ i ] == 1 ) { cout << "B" ; }
        else { cout << "R" ; }
    }
    cout << "\n" ;
}

int main ( ) {
    ios_base :: sync_with_stdio ( false ) ;
    cin.tie ( NULL ) ;
    int t = 1 ; cin >> t ;
    while ( t -- ) { solve ( ) ; }
    return 0 ;
}