#include <bits/stdc++.h>
#define int long long
using namespace std;
struct Event {
int x, id;
bool t;
Event(int x, bool t, int id) : x(x), t(t), id(id) {}
bool operator<(const Event &o) const {
if (x == o.x && t == o.t) return id < o.id;
if (x == o.x) return t > o.t;
return x < o.x;
}
};
int n, m;
vector<Event> e;
string ans;
bool check(int x) {
int lf = -1, rw = -1;
for (Event c : e) {
if (c.t) {
if (lf == -1) {
rw = c.x + x;
ans[c.id] = 'R';
} else {
if (c.x - lf > x) return 0;
lf = -1;
rw = c.x;
ans[c.id] = 'L';
}
} else {
if (c.x > rw && lf == -1) lf = c.x;
}
}
return lf == -1;
}
signed main() {
ios_base::sync_with_stdio(0); cin.tie(0);
cin >> n >> m;
for (int i = 0; i < n; i++) {
int x;
cin >> x;
e.emplace_back(x, 1, i);
}
for (int i = 0; i < m; i++) {
int x;
cin >> x;
e.emplace_back(x, 0, i);
}
for (int i = 0; i < n; i++) ans += '_';
sort(e.begin(), e.end());
int l = -1, r = 1e10;
while (r - l > 1) {
int md = (r + l) / 2;
if (check(md)) {
r = md;
} else {
l = md;
}
}
if (r == 1e10) {
cout << "-1\n";
} else {
check(r);
cout << r << "\n" << ans << "\n";
}
}
