#include <bits/stdc++.h>
using namespace std;
int main(){
int n,fn;cin>>n>>fn;
vector<int> s(n+1, 0), f(fn+1, -1);
for(int i=1;i<=n;i++){
cin>>s[i];
}
for(int i=1;i<=fn;i++){
cin>>f[i];
}
int hi=1e9, lo=0, ans=-1, m;
vector<int> dp(n+1, 0), prv(n+1, 0), st(n+1, 0);
auto solve=[&](int k) -> bool {
fill(dp.begin(),dp.end(),0);
fill(prv.begin(),prv.end(),0);
fill(st.begin(),st.end(),0);
vector<int> l(n+1, 0), r(n+1, 0), bef(n+1, 0), last(n+1, 0);
for(int i=1;i<=n;i++){
bef[i]=lower_bound(f.begin(),f.end(),s[i])-f.begin()-1;
last[i]=upper_bound(f.begin(),f.end(),s[i])-f.begin()-1;
r[i]=upper_bound(f.begin(),f.end(), s[i]+k)-f.begin()-1;
l[i]=lower_bound(f.begin(),f.end(), s[i]-k)-f.begin();
}
for(int i=1;i<=n;i++){
if (l[i] > dp[i-1] + 1) return 0;
dp[i]=last[i], prv[i]=i-1, st[i]=0;
if(dp[i-1] >= bef[i]){
dp[i]=r[i], prv[i]=i-1, st[i]=1;
}
if(i >= 2 and dp[i-2] >= l[i]-1){
if(r[i-1] > dp[i]){
dp[i]=r[i-1];
prv[i]=i-2;
st[i]=2;
}
}
}
if(dp[n] >= fn) return 1;
return 0;
};
while(hi >= lo){
m=(hi+lo)/2;
bool ok=solve(m);
if(ok){
ans=m;
hi=m-1;
}
else {
lo=m+1;
}
}
if(ans == -1){
cout<<-1;
return 0;
}
solve(ans);
vector<int> path;
int c=n;
while(c != 0){
path.push_back(c);
c = prv[c];
}
reverse(path.begin(),path.end());
cout<<ans<<'\n';
for(auto i : path){
if(st[i]==1) cout<<'R';
else if(st[i]==0)cout<<'L';
else cout<<"RL";
}
}
