#include <bits/stdc++.h>
/*
DP flowers
*/
int main(){
int n,m;
std::cin>>n>>m;
std::vector<int> sprinklers;
std::vector<int> flowers;
std::map<int,int> flowerinds;
for(int i=0;i<n;i++){
int x;
std::cin>>x;
sprinklers.push_back(x);
}
for(int i=0;i<m;i++){
int x;
std::cin>>x;
flowers.push_back(x);
flowerinds[x]=i;
}
flowerinds[2000000000]=m;
int lower=0,upper=1000000002;
while(1){
int kval=(lower+upper)/2-1;
if(lower+1>=upper){
if(lower==1000000001){
std::cout<<"-1\n";
return 0;
}else{
kval=lower;
}
}
std::vector<std::pair<int,int>> dp(n+1);
for(int i=0;i<n;i++){
std::pair<int,int> curval=dp[i];
dp[i+1]=std::max(dp[i+1],{curval.first,0});//do nothing
if(curval.first<m){
if(flowers[curval.first]>=sprinklers[i]-kval){
dp[i+1]=std::max(dp[i+1],{flowerinds.upper_bound(sprinklers[i])->second,-1});//left
}
if(flowers[curval.first]>=sprinklers[i]){
dp[i+1]=std::max(dp[i+1],{flowerinds.upper_bound(sprinklers[i]+kval)->second,1});//right
}
if(i+1<n&&sprinklers[i]<=sprinklers[i]+kval){//RL (no holes)
if(flowers[curval.first]>=sprinklers[i+1]-kval){
dp[i+2]=std::max(dp[i+2],{flowerinds.upper_bound(sprinklers[i]+kval)->second,2});
}
}
}
}
if(lower+1>=upper){
std::cout<<lower<<'\n';
std::string rec(n,' ');
int ind=n;
while(ind){
if(dp[ind].second==-1){
rec[ind-1]='L';
ind--;
}else if(dp[ind].second==1){
rec[ind-1]='R';
ind--;
}else if(dp[ind].second==2){//RL
rec[ind-1]='L';
rec[ind-2]='R';
ind-=2;
}else{//don't care ("do nothing")
rec[ind-1]='L';
ind--;
}
}
std::cout<<rec<<'\n';
return 0;
}
if(dp.back().first==m){
upper=kval+1;
}else{
lower=kval+1;
}
}
}
