#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define vi vector<ll>
#define vvi vector<vector<ll>>
#define vs vector<string>
#define vc vector<char>
#define vb vector<bool>
#define vp vector<pair<ll, ll>>
#define vpp vector<pair<ll, pair<ll, ll>>>
#define pp pair<ll, ll>
#define qi queue<ll>
#define qp queue<pp>
#define pqi priority_queue<ll>
#define pqp priority_queue<pp>
#define mi map<ll, ll>
#define mpi map<pp, ll>
#define mip map<ll, pp>
#define mp map<pp, pp>
#define mb map<ll, bool>
#define si set<ll>
#define sp set<pp>
#define sc set<char>
#define mod 1000000007
#define inf 1000000000000000000
#define all(x) (x).begin(), (x).end()
ll n, m;
vi a, b;
mi sprink;
vi pref;
ll mxPos;
vi comp2;
ll dist(ll x, ll y) {
return comp2[x] - comp2[y];
}
string solve(ll k) {
if(n == 1) {
if(b[0] < a[0] && b.back() > a[0]) {
return "";
}
ll need = max(abs(dist(b[0], a[0])), abs(dist(b.back(), a[0])));
if(need > k) return "";
if(b[0] < a[0]) return "L";
return "R";
}
if(dist(a[0], b[0]) > k) return "";
vvi dp(n, vi(2, -inf));
vvi prv(n, vi(2, -1));
dp[0][0] = pref[a[0]];
if(pref[a[0]] == 0) {
ll last = upper_bound(all(comp2), comp2[a[0]] + k) - comp2.begin() - 1;
dp[0][1] = pref[last + 1];
}
else dp[0][1] = 0;
for(int i = 1; i < n; i++) {
ll x = a[i], y = a[i - 1];
for(int j = 0; j < 2; j++) {
for(int prev = 0; prev < 2; prev++) {
if(dp[i - 1][prev] == -inf) continue;
ll last = dp[i - 1][prev];
if(last == m) {
dp[i][j] = m;
prv[i][j] = prev;
continue;
}
ll firstFlower = b[last];
if(j == 0) {
if(dist(x, firstFlower) > k) continue;
if(prev == 0) {
ll newVal = pref[x];
if(newVal > dp[i][j]) {
dp[i][j] = newVal;
prv[i][j] = prev;
}
}
else {
ll end = upper_bound(all(comp2), comp2[y] + k) - comp2.begin();
ll newVal = max(pref[x], pref[end]);
if(newVal > dp[i][j]) {
dp[i][j] = newVal;
prv[i][j] = prev;
}
}
}
else {
if(prev == 0) {
if(firstFlower < x) {
if(last > dp[i][j]) {
dp[i][j] = last;
prv[i][j] = prev;
}
}
else {
ll end = upper_bound(all(comp2), comp2[x] + k) - comp2.begin();
if(pref[end] > dp[i][j]) {
dp[i][j] = pref[end];
prv[i][j] = prev;
}
}
}
else {
if(firstFlower < y) continue;
if(firstFlower < x) {
if(last > dp[i][j]) {
dp[i][j] = last;
prv[i][j] = prev;
}
}
else {
ll end = upper_bound(all(comp2), comp2[x] + k) - comp2.begin();
if(pref[end] > dp[i][j]) {
dp[i][j] = pref[end];
prv[i][j] = prev;
}
}
}
}
}
}
}
ll from = -1;
for(int i = 0; i < 2; i++) {
if(dp[n - 1][i] == m) {
from = i;
}
}
if(from == -1) return "";
ll i = n - 1;
string ans;
while(from != -1) {
if(from == 0) ans += "L";
else ans += "R";
from = prv[i][from];
i--;
}
reverse(all(ans));
return ans;
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cin >> n >> m;
a = vi(n), b = vi(m);
for(int i = 0; i < n; i++) cin >> a[i];
for(int i = 0; i < m; i++) cin >> b[i];
if(m == 0) {
cout << "0\n";
for(int i = 0; i < n; i++) cout << "R";
cout << '\n';
return 0;
}
if(n == 0) {
cout << "-1\n";
return 0;
}
si vals;
for(auto x : a) vals.insert(x);
for(auto x : b) vals.insert(x);
mi comp;
for(auto x : vals) {
comp[x] = comp.size();
comp2.push_back(x);
}
for(int i = 0; i < n; i++) a[i] = comp[a[i]];
for(int i = 0; i < m; i++) b[i] = comp[b[i]];
for(auto x : a) {
sprink[x]++;
}
vi newB;
for(int i = 0; i < m; i++) {
if(sprink.count(b[i])) continue;
if(newB.size() > 0 && newB.back() == b[i]) continue;
newB.push_back(b[i]);
}
b = newB;
m = b.size();
if(m == 0) {
cout << "0\n";
for(int i = 0; i < n; i++) cout << "R";
cout << '\n';
return 0;
}
mxPos = vals.size();
pref = vi(mxPos + 1, 0);
ll ind = 0;
for(int i = 0; i < mxPos; i++) {
pref[i + 1] = pref[i];
while(ind < m && b[ind] == i) {
pref[i + 1]++;
ind++;
}
}
ll ans = -1;
string s;
ll l = 0, r = INT_MAX;
while(l <= r) {
ll d = (l + r) / 2;
string cur = solve(d);
if(cur != "") {
ans = d;
s = cur;
r = d - 1;
}
else l = d + 1;
}
cout << ans << '\n';
if(ans != -1) cout << s << '\n';
return 0;
}
