#include<bits/stdc++.h>
#define int long long
using namespace std;
string ansstr;
bool check(int x, vector<int> a, vector<int> b)
{
string curstr;
int maximum = -1e9;
reverse(b.begin(), b.end());
for(int i = 0; i < a.size(); i++) if(a[i] < b.back()){
maximum = a[i]+x; curstr += "R";
}
while(b.size() > 0){
while(a.size() > curstr.size() && a[curstr.size()] <= b.back()){
maximum = a[curstr.size()] + x; curstr += "R";
}
while(b.size() > 0 && b.back() <= maximum) b.pop_back();
if(b.size() == 0) break;
int nepl = b.back()+x, p = upper_bound(a.begin(), a.end(), nepl) - a.begin() - 1;
if(p < curstr.size() || p > a.size()) return 0;
int lastval = -1;
while(b.size() > 0 && b.back() <= a[p]){
lastval = b.back(); b.pop_back();
}
while(a.size() > curstr.size() && a[curstr.size()] < lastval){
maximum = a[curstr.size()]+x;
curstr += "R";
}
curstr += "L";
}
ansstr = curstr;
return 1;
}
signed main()
{
ios_base::sync_with_stdio(false);
cin.tie(0);
int n, m;
cin>>n>>m;
vector<int> a(n), b;
for(int i = 0; i < n; i++) cin>>a[i];
for(int i = 0; i < m; i++){
int x; cin>>x;
if(x > a.back() || *lower_bound(a.begin(), a.end(), x) != x) b.push_back(x);
}
int l = 0, r = 1e9, ans = -1;
string str;
while(l <= r){
int mid = (l+r)/2;
if(check(mid, a, b) == 1){ans = mid; r = mid-1;}
else l = mid+1;
}
cout<<ans<<'\n';
if(ans > -1) cout<<ansstr;
}
