#include<bits/stdc++.h>
#define int long long
#define f0r(i,n) for(int i = 0; i < n; i++)
#define FOR(i,k,n) for(int i = k; i < n; i++)
#define pb push_back
#define mp make_pair
#define eb emplace_back
#define F first
#define S second
#define vi vector<int>
#define pii pair<int,int>
#define out(x) cout<<x<<'\n'
#define dout(x) cout<<x<<' '<<#x<<endl
#define dout2(x,y) cout<<x<<' '<<#x<<' '<<y<<' '<<#y<<endl
#define vout(v) cout<<#v<<": "; for(auto u : v)cout<<u<<' '; cout<<endl
using namespace std;
const int mxn = 1e5 + 5;
int n,m; vi a,b; vector<pii>w;
string solve(int k){
vi x, y; bool ok = 1; string ans; f0r(i,n+m){
if(i > 0 && w[i].S == 0 && w[i-1].S == 0){
int ptr = 0; bool skip = 0; f0r(j,x.size()){
if(skip){skip=0; continue;}
if(ptr == y.size())ans+='L'; else if(y[ptr] > x[j]){
ans += 'R'; while(ptr < y.size() && y[ptr] <= x[j] + k)ptr++;
} else{
if(j < x.size() - 1 && x[j+1] - k <= y[ptr]){
while(ptr < y.size() && y[ptr] <= x[j] + k)ptr++; skip=1; ans += "RL";
}
else if(y[ptr] < x[j] - k){
ok = 0; break;
}
else{
while(ptr < y.size() && y[ptr] <= x[j])ptr++; ans += 'L';
}
}
}
if(ptr < y.size())ok = 0;
x.clear(),y.clear();
}
if(w[i].S == 0)x.pb(w[i].F); else y.pb(w[i].F);
}
int ptr = 0; bool skip = 0; f0r(j,x.size()){
if(skip){skip=0; continue;}
if(ptr == y.size())ans+='L'; else if(y[ptr] > x[j]){
ans += 'R'; while(ptr < y.size() && y[ptr] <= x[j] + k)ptr++;
} else{
if(j < x.size() - 1 && x[j+1] - k <= y[ptr]){
while(ptr < y.size() && y[ptr] <= x[j] + k)ptr++; skip=1; ans += "RL";
}
else if(y[ptr] < x[j] - k){
ok = 0; break;
}
else{
while(ptr < y.size() && y[ptr] <= x[j])ptr++; ans += 'L';
}
}
}
if(ptr < y.size())ok = 0;
x.clear(),y.clear();
if(ok)return ans; else return "G";
}
signed main(){
cin>>n>>m; a.resize(n); set<int>s; f0r(i,n)cin>>a[i],s.insert(a[i]); f0r(i,m){int x; cin>>x; if(!s.count(x))b.pb(x);}
m = b.size(); f0r(i,n)w.eb(a[i],0); f0r(i,m)w.eb(b[i],1);
sort(w.begin(),w.end()); int lo = 0, hi = 1e9 + 5; while(lo < hi){
int mid = lo + (hi - lo) / 2; string s = solve(mid); if(s[0]=='G')lo=mid+1; else hi=mid;
}
if(lo == 1e9+5)out(-1); else{
string ans = solve(lo); out(lo); out(ans);
}
}
