// #include <bits/stdc++.h>
#include <iostream>
#include <cmath>
#include <algorithm>
#include <map>
#include <vector>
#include <iomanip>
#include <string>
#include <queue>
#include <set>
#include <deque>
using namespace std;
#define int long long
#define endl "\n";
const int N=2e5+5;
const int M=1e9+7;
void solve()
{
int n,m;
cin >> n >> m;
vector<int>a(n),b(m);
for (int i=0;i<n;i++){
cin >> a[i];
}
for (int i=0;i<m;i++){
cin >> b[i];
}
if (n==1 and a[0]>b[0] and a[0]<b[m-1]){
cout << -1 << endl;
return;
}
int l=0;
int h=b[m-1]+1;
int mi=(l+h)/2;
while (l<h){
queue<int>o;
for (int p:b){
o.push(p);
}
for (int i:a){
if (!o.empty()){
int he=o.front();
if (he<i){
while (!o.empty()){
he=o.front();
if (he>=i-mi and he<=i){
o.pop();
}
else{
break;
}
}
}
else{
while (!o.empty()){
he=o.front();
if (he<=i+mi and he>=i){
o.pop();
}
else{
break;
}
}
}
}
}
if (o.empty()){
h=mi;
}
else{
l=mi+1;
}
mi=(l+h)/2;
}
string s;
queue<int>o;
for (int p:b){
o.push(p);
}
for (int i:a){
if (!o.empty()){
int he=o.front();
if (he<i){
s+='L';
while (!o.empty()){
he=o.front();
if (he>=i-mi and he<=i){
o.pop();
}
else{
break;
}
}
}
else{
s+='R';
while (!o.empty()){
he=o.front();
if (he<=i+mi and he>=i){
o.pop();
}
else{
break;
}
}
}
}
else{
s+='R';
}
}
cout << mi << endl;
cout << s << endl;
}
signed main()
{
ios::sync_with_stdio(0);//DO NOT USE IN INTERACTIVE
cin.tie(0), cout.tie(0);//DO NOT USE IN INTERACTIVE
cout << fixed<<setprecision(9);
int t=1;
// cin >> t;
for (int _=1;_<=t;_++){
solve();
}
}
