#include "bits/stdc++.h"
#define int long long
#define all(v) v.begin() , v.end()
#define sz(a) (int)a.size()
using namespace std;
int n,m;
vector<int> a,b;
void _(){
cin >> n >> m;
for(int i=0;i<n;i++){
int x; cin >> x;
a.push_back(x);
}
for(int i=0;i<m;i++){
int x;cin >> x;
b.push_back(x);
}
auto get = [&](int ll,int rr){
if(ll>rr) return -1LL;
int it = lower_bound(all(b),rr+1)-b.begin();
int it2 = lower_bound(all(b),ll)-b.begin();
return it-it2;
};
auto check = [&](int pow)->pair<bool,vector<char>>{
int p=0;
vector<char> res(n,'L');
for(int i=0;i<m;){
if(p==n) return {0,res};
int lol=-1;
while(p<n && a[p]<=b[i]){
res[p]='R';
lol=max(lol,a[p]+pow);
p++;
}
if(lol>=b[i]){
while(i<m && lol>=b[i]) i++;
continue;
}
if(i==m) return {1,res};
if(p==n) return {0,res};
vector<int> f;
while(p<n && a[p]-pow<=b[i]) f.push_back(p++);
if(sz(f)==0) return {0,res};
if(sz(f)==1){
if(a[f[0]]==b[i]){
res[f[0]]='R';
while(i<m && b[i]<=a[f[0]]+pow) i++;
}
else while(i<m && b[i]<=a[f[0]]) i++;
continue;
}
if(sz(f)>=3){
for(int j=0;j<sz(f);j++){
if(j==sz(f)-2) continue;
res[f[j]]='R';
}
while(i<m && b[i]<=a[f.back()]+pow) i++;
if(i==m) return {1,res};
continue;
}
if(get(a[f[0]]+1,a[f[1]]-1)>0){
res[f[0]]='R';
while(i<m && b[i]<=a[f[0]]+pow) i++;
}
else{
res[f[1]]='R';
while(i<m && b[i]<=a[f[1]]+pow) i++;
}
}
return {1,res};
};
int l=0,r=(int)1e18;
while(l<r){
int m=(l+r)/2;
if(check(m).first) r=m;
else l=m+1;
}
if(r==(int)1e18) cout << -1 << '\n';
else{
auto X = check(l);
cout << l << '\n';
for(char x:X.second) cout << x;
cout << '\n';
}
}
int32_t main(){
cin.tie(0); ios::sync_with_stdio(0);
int tc=1;//cin >> tc;
while(tc--) _();
return 0;
}
