#include <bits/stdc++.h>
using namespace std;
using ll = long long;
void solve() {
int n, m;
cin >> n >> m;
vector<ll> s(n), f(m);
for (auto &e : s) {
cin >> e;
}
for (auto &e : f) {
cin >> e;
}
if (n == 1) {
auto mn = *min_element(f.begin(), f.end());
auto mx = *max_element(f.begin(), f.end());
if (mn < s[0] and s[0] < mx) {
cout << -1 << endl;
return;
}
}
auto sol = [&](ll k, bool retrieve = false) {
vector<int> dp(n + 1, 0);
vector<vector<int>> del_list(n + 1);
set<int> se;
vector<int> prv(n + 1, -1);
auto update = [&](int i, int pos, int p) {
if (dp[i] < pos) {
dp[i] = pos;
prv[i] = p;
}
};
for (int i = 0; i < n; ++i) {
for (auto e : del_list[i]) {
se.erase(e);
}
if (not se.empty()) {
int pos = upper_bound(f.begin(), f.end(), s[i - 1] + k) - f.begin();
update(i + 1, pos, *se.begin());
}
auto j = dp[i];
if (j == m) {
update(i + 1, m, i);
continue;
}
if (s[i] < f[j]) {
int pos = upper_bound(f.begin(), f.end(), s[i] + k) - f.begin();
update(i + 1, pos, i);
} else {
int pos = upper_bound(s.begin(), s.end(), f[j] + k) - s.begin();
if (i < pos) {
se.insert(i);
del_list[pos].push_back(i);
}
if (f[j] + k >= s[i]) {
int pos = upper_bound(f.begin(), f.end(), s[i]) - f.begin();
update(i + 1, pos, -1);
}
}
}
if (not retrieve) {
return dp;
}
vector<int> res(n);
int cur = n;
while (cur != 0) {
int p = prv[cur];
cerr << cur << ' ' << p << endl;
if (p == -1) {
p = cur - 1;
res[p] = -1;
} else if (p == cur - 1) {
res[p] = 1;
} else {
for (int i = p; i < cur - 1; ++i) {
res[p] = 1;
}
res[cur - 1] = -1;
}
cur = p;
}
return res;
};
ll ok = 1ll << 30, ng = -1;
while (ok - ng > 1) {
auto md = (ok + ng) / 2;
auto res = sol(md);
if (res[n] == m) {
ok = md;
} else {
ng = md;
}
}
cout << ok << endl;
auto res = sol(ok, true);
for (auto e : res) {
cout << (e == -1 ? 'L' : 'R');
}
cout << endl;
}
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
solve();
return 0;
}
