#include<bits/stdc++.h>
#define taskname "C"
using namespace std;
const int INF = 1e9 + 1;
const int lim = 1e5 + 5;
template<class T>void minimize(T& a, T b){
if(a > b){
a = b;
}
}
int n, m, s[lim], f[lim];
namespace sub1{
void solve(){
if(f[1] < s[1] && s[1] < f[m]){
return void(cout << -1);
}
if(s[1] <= f[1]){
cout << f[m] - s[1] << "\nR";
}
else{
cout << s[1] - f[1] << "\nL";
}
}
}
namespace sub2{
void solve(){
int low = 1, high = INF, ans;
while(low <= high){
int mid = (low + high) >> 1;
vector<int>cnt(m + 2, 0);
for(int i = 1; i < n; i += 3){
cnt[lower_bound(f + 1, f + m + 1, s[i + 1] - mid) - f]++;
cnt[upper_bound(f + 1, f + m + 2, s[i + 1] + mid) - f]--;
}
bool flag = true;
for(int i = 1; i <= m; i++){
if((cnt[i] += cnt[i - 1]) == 0){
flag = false;
break;
}
}
if(flag){
high = (ans = mid) - 1;
}
else{
low = mid + 1;
}
}
cout << ans << "\n";
for(int i = 1; i < n; i += 3){
cout << "LRL";
}
}
}
namespace sub3{
void solve(){
int ans_k = INF, ans_mask = -1;
for(int mask = (1 << n) - 1; mask > -1; mask--){
int low = 1, high = ans_k - 1;
while(low <= high){
int mid = (low + high) >> 1;
vector<int>cnt(m + 2, 0);
for(int i = 0; i < n; i++){
if(1 << i & mask){
cnt[lower_bound(f + 1, f + m + 1, s[i + 1] - mid) - f]++;
cnt[upper_bound(f + 1, f + m + 2, s[i + 1]) - f]--;
}
else{
cnt[lower_bound(f + 1, f + m + 1, s[i + 1]) - f]++;
cnt[upper_bound(f + 1, f + m + 2, s[i + 1] + mid) - f]--;
}
}
bool flag = true;
for(int i = 1; i <= m; i++){
if((cnt[i] += cnt[i - 1]) == 0){
flag = false;
break;
}
}
if(flag){
high = (ans_k = mid) - 1;
ans_mask = mask;
}
else{
low = mid + 1;
}
}
}
if(ans_mask == -1){
return void(cout << -1);
}
cout << ans_k << "\n";
for(int i = 0; i < n; i++){
cout << ((1 << i & ans_mask) ? 'L' : 'R');
}
}
}
namespace sub45{
void solve(){
int low = 1, high = INF, ans = -1;
while(low <= high){
int mid = (low + high) >> 1, i = 1, j = 1, r = s[1];
bool flag = true;
for(; i <= n; i++){
if(f[j] >= s[i]){
while(f[j] <= s[i] + mid){
j++;
}
}
else if(f[j] < s[i] - mid){
flag = false;
break;
}
else if(s[i + 1] - mid <= f[j] && *upper_bound(f + 1, f + m + 2, s[i]) <= s[i + 1]){
r = s[i] + mid;
}
else{
while(f[j] <= max(r, s[i])){
j++;
}
}
}
if(!flag || j <= m){
low = mid + 1;
}
else{
high = (ans = mid) - 1;
}
}
cout << ans << "\n";
if(ans != -1){
for(int i = 1, j = 1, r = s[1]; i <= n; i++){
if(f[j] >= s[i]){
while(f[j] <= s[i] + ans){
j++;
}
cout << "R";
}
else if(s[i + 1] - ans <= f[j]){
r = s[i] + ans;
cout << "R";
}
else{
while(f[j] <= max(r, s[i])){
j++;
}
cout << "L";
}
}
}
}
}
int main(){
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
if(fopen(taskname".inp", "r")){
freopen(taskname".inp", "r", stdin);
}
cin >> n >> m;
bool is_sub2 = bool(n % 3 == 0);
for(int i = 1; i <= n; i++){
cin >> s[i];
if(i % 3 == 0 && s[i] != s[i - 2]){
is_sub2 = false;
}
}
for(int i = 1; i <= m; i++){
cin >> f[i];
}
f[m + 1] = s[n + 1] = INF << 1;
sub45::solve();
return 0;
if(n == 1){
sub1::solve();
}
else if(is_sub2){
sub2::solve();
}
else if(n <= 10 && m <= 1000){
sub3::solve();
}
else{
sub45::solve();
}
}
