#include <bits/stdc++.h>
#pragma GCC optimize("O3,unroll-loops")
#define pb push_back
#define F first
#define pii pair<ll,ll>
#define all(a) a.begin(),a.end()
#define S second
#define sz(a) (int)a.size()
#define rep(i , a , b) for(int i = (a) ; i <= (b) ; i++)
#define per(i , a , b) for(int i = (a) ; i >= (b) ; i--)
#define ld double
#define ll long long
using namespace std ;
const int maxn = 1e6 + 10, inf = 1e9+ 10 , mod = 1e9 + 9 ;
int s[maxn] , t[maxn] , dp[maxn] , par[maxn];
char ans[maxn] ;
int n , m;
int find(int x){
int l = 0, r = m+1 ;
while(r-l>1){
int mid = (l+r)/2 ;
if(t[mid] >= x)r = mid ;
else l = mid ;
}
return r ;
}
bool ch(int k ){
rep(i ,1 , n){
dp[i] = dp[i-1] ;
par[i] = 0 ;
int id =t[dp[i-1]+1];
if(id <= s[i]){
if(abs(id-s[i]) <= k){
dp[i] = find(s[i]+1) - 1 ;
par[i] = 1;
}
}
if(id >= s[i]){
if(dp[i] < find(s[i]+k+1)-1){ dp[i] = find(s[i]+k+1) - 1 ; par[i] = 2; }
}
if(i > 1){
id = t[dp[i-2]+1];
if(id <= s[i] && s[i]-id <= k){
if(dp[i] < find(s[i-1] + k + 1) - 1){
dp[i] = max(dp[i] , find(s[i-1] + k + 1) - 1);
par[i] =3 ;
}
}
}
if(dp[i] == m)return 1 ;
}
return 0 ;
}
signed main(){
ios_base::sync_with_stdio(0) ; cin.tie(0) ;
cin >> n >> m ;
rep(i ,1, n){
cin >> s[i] ;
}
rep(i ,1 , m){
cin >> t[i] ;
}
int l =-1 , r = inf ;
while(r-l>1){
int mid = (l+r)/2 ;
if(ch(mid) == 1)r =mid ;
else l = mid ;
}
if(r == inf){
cout << "-1\n";
}else{
ch(r) ;
cout << r << "\n";
int x = n;
while(x){
if(par[x] <= 2){
if(par[x] <= 1){
ans[x] = 'L';
}else{
ans[x] = 'R' ;
}
x--;
}else{
ans[x-1] = 'R' ;
ans[x] = 'L' ;
x-=2 ;
}
}
rep(i ,1, n)cout << ans[i] ;
cout << "\n";
}
}
/*
*/
