#include <iostream>
#include <algorithm>
using namespace std;
const int N = 2e5;
int a[N], b[N], Mx[N], Par[N], type[N], dir[N], n, m;
void update(int i, int j, int val, int tp){
if (Mx[j] >= val)
return;
Mx[j] = val;
Par[j] = i;
type[j] = tp;
}
bool check(int K, bool print = 0){
for (int i=1;i<=n + 1;i++)
Mx[i] = 1;
for (int i=1;i<=n;i++){
update(i-1, i, Mx[i-1], 1);
// Mx[i] = max(Mx[i], Mx[i-1]);
if (Mx[i] < m + 1 and b[Mx[i]] < Mx[i-1] and a[i] - K <= b[Mx[i]]){
int u = upper_bound(b, b + m + 1, a[i]) - b;
update(i, i + 1, u, 1);
// Mx[i + 1] = max(Mx[i + 1], u);
}
if (Mx[i] < m + 1 and b[Mx[i]] >= a[i]){
int u = upper_bound(b, b + m + 1, a[i] + K) - b;
update(i, i + 1, u, 2);
// Mx[i + 1] = max(Mx[i + 1], u);
}
if (Mx[i] < m + 1 and i < n and a[i + 1] - K <= b[Mx[i] + 1]){
int u = upper_bound(b, b + m + 1, a[i] + K) - b;
update(i, i + 2, u, 3);
// Mx[i + 2] = max(Mx[i + 2], u);
}
}
if (print){
int nn = n;
while (n){
if (type[n] > 1)
dir[Par[n]] = 1;
n = Par[n];
// cout<<n<<endl;
}
cout<<K<<'\n';
for (int i=1;i<=nn;i++)
cout<<(dir[i] ? 'R' : 'L');
cout<<'\n';
exit(0);
}
return max(Mx[n], Mx[n + 1]) >= m + 1;
}
int main(){
cin>>n>>m;
for (int i=1;i<=n;i++)
cin>>a[i];
for (int i=1;i<=m;i++)
cin>>b[i];
b[m + 1] = 2.1e9;
if (n == 1 and a[1] > b[1] and a[1] < b[m])
return cout<<"-1\n", 0;
// for (int i=1;i<=10;i++)
// cout<<check(i)<<'\n';
// check(6, 1);
int l = -1, r = 1e9 + 10;
while (l + 1 < r){
int mid = (l + r) / 2;
if (check(mid))
r = mid;
else
l = mid;
}
check(r, 1);
}
