#include <bits/stdc++.h>
#define endl '\n'
#define ld long double
#define pb push_back
#define pf push_front
#define mod 998244353
#define se second
#define fi first
#define all(ls) (ls).begin(),(ls).end()
#define int long long
using namespace std;
int n,m,works;
const int N=1e5+10;
int s[N],f[N],d[N];
void work(int mid){
works=0;
set<int>rem;
for(int i=0;i<n;i++)
d[i]=0;
for(int i=0;i<m;i++)
rem.insert(f[i]);
for(int i=0;i<n;i++){
if(rem.empty()){
works=1;
return;
}
int cur=*rem.begin();
if(cur>=s[i])
d[i]=1;
else if(cur<(s[i]-mid)){
works=0;
return;
}
else if(cur>=(s[i]-mid))
d[i]=0;
else{
auto up=rem.upper_bound(s[i]);
if(up==rem.end())
d[i]=0;
else if(*up>=s[i+1])
d[i]=0;
else
d[i]=1;
}
if(d[i]==0){
//s[i]-mid....j....s[i]
while(rem.size() and (s[i]-mid)<=*rem.begin() and *rem.begin()<=s[i])
rem.erase(rem.begin());
}
if(d[i]==1){
//s[i]....j....s[i]+mid
auto ptr=rem.lower_bound(s[i]);
while(rem.size() and ptr!=rem.end() and s[i]<=(*ptr) and (*ptr)<=(s[i]+mid))
ptr=rem.erase(ptr);
}
}
works=(rem.empty());
}
void solve(){
cin>>n>>m;
for(int i=0;i<n;i++)
cin>>s[i];
for(int i=0;i<m;i++)
cin>>f[i];
int low=0,high=1e14;
while(low<=high){
int mid=(low+high)/2;
work(mid);
if(works)
high=mid-1;
else
low=mid+1;
}
if(low==(1e14+1))
low=-1;
cout<<low<<endl;
if(low!=-1){
work(low);
for(int i=0;i<n;i++){
if(d[i]==0)
cout<<'L';
else
cout<<'R';
}
cout<<endl;
}
}
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int t=1;
// cin>>t;
for(int i=1;i<=t;i++){
// cout<<"Scenario #"<<i<<":"<<" ";
solve();
}
}
