#include<bits/stdc++.h>
using namespace std;
#define ll long long int
#define pb push_back
#define en cout << '\n'
#define vi vector<int>
#define pii pair<int, int>
#define ff first
#define ss second
#define all(x) x.begin(),x.end()
const int N = 1e5+100;
int n, m, a[N], b[N];
int get(int l, int r){
if(r < l) return 0;
return upper_bound(b+1, b+1+m, r) - lower_bound(b+1, b+1+m, l);
}
void solve(){
cin >> n >> m;
vector<pii> v;
for(int i = 1; i <= n; ++i){
cin >> a[i];
v.pb({a[i], 1});
}
for(int i = 1; i <= m; ++i){
cin >> b[i];
v.pb({b[i], 0});
}
sort(all(v));
string soll;
int l = 0, r = 1e9, ans = -1;
while(l <= r){
int k = l+r>>1;
string sol = "";
bool ok = 1;
int last_covered = -2e9;
for(int i = 1; i <= n; ++i){
if(last_covered >= a[i] - 1){
sol += 'R';
last_covered = a[i] + k;
continue;
}
if(get(last_covered + 1, a[i] - 1) > get(a[i] - k, a[i] - 1)){
ok = 0;
break;
}
if(get(last_covered + 1, a[i] - 1) > 0){
if(i + 1 <= n && get(a[i] + 1, min(a[i + 1] - 1, a[i] + k)) == 0){
sol += 'L';
last_covered = a[i];
}else if(i + 1 <= n && get(a[i] + 1, min(a[i + 1] - 1, a[i] + k)) > 0){
if(a[i + 1] - k < a[i] && get(last_covered + 1, a[i] - 1) <= get(a[i + 1] - k, a[i] - 1)){
sol += 'R';
sol += 'L';
last_covered = a[i] + k;
++i;
continue;
}else{
sol += 'L';
sol += 'L';
last_covered = a[i + 1];
if(get(a[i] + 1, a[i + 1] - k - 1) > 0){
ok = 0;
break;
}
++i;
continue;
}
}else{
sol += 'L';
last_covered = a[i];
}
}else{
sol += 'R';
last_covered = a[i] + k;
}
}
if(b[m] > last_covered) ok = 0;
if(ok){
ans = k;
soll = sol;
r = k - 1;
}else{
l = k + 1;
}
}
cout << ans << '\n';
if(ans != -1){
cout << soll;
}
}
int main(){
cin.tie(0); ios::sync_with_stdio(0);
solve();
return 0;
}
