#include <bits/stdc++.h>
using namespace std;
#define int long long
signed main(){
ios::sync_with_stdio(0);
cin.tie(0);
int n,m;
cin >> n >> m;
int s[n];
for(int i = 0;i<n;i++){
cin >> s[i];
}
int f[m];
for(int i = 0;i<m;i++){
cin >> f[i];
}
char ans[n];
auto exist = [&] (int l, int r){
//checks if flower exists between l and r
//inclusive
if(l>r){
return 0;
}
int lef = lower_bound(f,f+m,l)-f;
int rig = upper_bound(f,f+m,r)-f-1;
if(lef<=rig){
return 1;
}
else{
return 0;
}
};
auto check = [&] (int k){
array<int,2> dp[n];
//stores furthest point covered from 0
//states = {R,L}
array<int,2>backtrack[n];
if(s[0]<=f[0]){
//facing left is quite pointless but ok
dp[0][0]=s[0]+k;
dp[0][1]=s[0];
}
else{
//sprinkler is ahead
//facing R will miss
dp[0][0]=-1;
dp[0][1]=s[0];
}
backtrack[0][0]=-1;
backtrack[0][1]=-1;
for(int i = 1;i<n;i++){
backtrack[i][0]=-1;
backtrack[i][1]=-1;
dp[i][0]=max(dp[i-1][0],dp[i-1][1]);
dp[i][1]=max(dp[i-1][0],dp[i-1][1]);
if(dp[i][0]==dp[i-1][0]){
backtrack[i][0]=0;
backtrack[i][1]=0;
}
else{
backtrack[i][0]=1;
backtrack[i][1]=1;
}
//check if I make this R
///transition from previous R
if(!exist(dp[i-1][0]+1,s[i]-1)){
//holes covered
dp[i][0]=s[i]+k;
backtrack[i][0]=0;
}
//transition form previous L
if(!exist(dp[i-1][1]+1,s[i]-1)){
//holes covered
dp[i][0]=s[i]+k;
backtrack[i][0]=1;
}
//check if I make this L
//transition form previous L
if(!exist(dp[i-1][1]+1,s[i]-k-1)){
//holes covered
dp[i][1]=max(s[i],dp[i-1][1]);
backtrack[i][1]=1;
}
//transition from previous R
if(!exist(dp[i-1][0]+1,s[i]-k-1)){
//holes covered
dp[i][1]=max(s[i],s[i-1]+k);
backtrack[i][1]=0;
}
}
if(max(dp[n-1][0],dp[n-1][1])>=f[m-1]){
//covered so reconstruct
int state = 0;
if(dp[n-1][1]>=f[m-1]){
state=1;
}
for(int i = n-1;i>=0;i--){
if(state==0){
ans[i]='R';
}
else{
ans[i]='L';
}
state=backtrack[i][state];
}
return 1;
}
return 0;
};
int lo = 0;
int hi = 2e9;
while(lo<hi){
int mid = (lo+hi)/2;
if(check(mid)){
hi=mid;
}
else{
lo=mid+1;
}
}
if(lo==2e9){
cout << -1;
return 0;
}
check(lo);
cout << lo << "\n";
for(int i = 0;i<n;i++){
cout << ans[i];
}
return 0;
}
