#include <bits/stdc++.h>
typedef long long ll;
#define FOR(i,x,y) for(ll i=x; i<y; i++)
#define FORNEG(i,x,y) for(ll i=x; i>y; i--)
using namespace std;
ll dp[100005];
string prevs[100005];
int main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
ll n,m;
cin >> n >> m;
FOR(i,0,n+1) dp[i] = -1;
vector<ll> water(n);
vector<ll> flower(m);
FOR(i,0,n) cin >> water[i];
FOR(i,0,m) cin >> flower[i];
ll lo = 0, hi = 10000000000000000;
while (lo < hi){
FOR(i,0,n+1) dp[i] = -1;
ll k = (lo+hi)/2;
bool flag = false;
FOR(i,0,n){
ll sus = upper_bound(flower.begin(), flower.end(), dp[i]) - flower.begin();
if (sus >= m || flower[sus] >= water[i]){
if (water[i] + k > dp[i+1]){
dp[i+1] = water[i] + k;
prevs[i+1] = "R";
}
}else{
if (abs(flower[sus] - water[i]) > k){
flag = true;
}
if (i==n-1){
if (water[i] > dp[i+1]){
dp[i+1] = water[i];
prevs[i+1] = "L";
}
}
else{
if (abs(flower[sus] - water[i+1]) > k){
if (water[i] > dp[i+1]){
dp[i+1] = water[i];
prevs[i+1] = "L";
}
}else{
if (water[i] > dp[i+1]){
dp[i+1] = water[i];
prevs[i+1] = "L";
}
ll maxi = max(water[i]+k, water[i+1]);
if (maxi > dp[i+2]){
dp[i+2] = maxi;
prevs[i+2] = "LR";
}
}
}
}
}
if (dp[n] < flower[m-1]) flag = 1;
if (flag==0) hi = k;
else lo = k+1;
}
ll k = lo;
FOR(i,0,n+1) dp[i] = -1;
FOR(i,0,n){
ll sus = upper_bound(flower.begin(), flower.end(), dp[i]) - flower.begin();
//cout << dp[i] << " "<< sus << endl;
if (sus >= m || flower[sus] >= water[i]){
if (water[i] + k > dp[i+1]){
dp[i+1] = water[i] + k;
prevs[i+1] = "R";
}
}else{
if (i==n-1){
if (water[i] > dp[i+1]){
dp[i+1] = water[i];
prevs[i+1] = "L";
}
}
else{
if (abs(flower[sus] - water[i+1]) > k){
if (water[i] > dp[i+1]){
dp[i+1] = water[i];
prevs[i+1] = "L";
}
}else{
if (water[i] > dp[i+1]){
dp[i+1] = water[i];
prevs[i+1] = "L";
}
ll maxi = max(water[i]+k, water[i+1]);
if (maxi > dp[i+2]){
dp[i+2] = maxi;
prevs[i+2] = "LR";
}
}
}
}
}
ll cur = n;
string ans = "";
while (cur != 0){
ans += prevs[cur];
cur -= prevs[cur].size();
}
reverse(ans.begin(), ans.end());
if (lo == 10000000000000000) cout << -1;
else{
cout << lo << endl;
cout << ans << endl;
}
}
