#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define vc vector
#define st first
#define nd second
#define pll pair<ll, ll>
#define sz(a) (ll)a.size()
#define all(a) a.begin(), a.end()
#define pub push_back
#define pob pop_back
ll n, m;
vc<ll> a, b;
string str;
void input() {
cin >> n >> m;
a.resize(n);
b.resize(m);
for (ll &ai : a)
cin >> ai;
for (ll &bi : b)
cin >> bi;
}
bool check(ll k) {
queue<ll> q;
for (ll &bi : b)
q.push(bi);
str.clear();
for (ll i = 0; i < n; i++) {
ll l, r;
if (q.empty() or a[i] <= q.front()) {
str.pub('R');
l = a[i];
r = a[i] + k;
} else if (a[i] - k <= q.front()) {
str.pub('L');
l = a[i] - k;
r = a[i];
} else
return false;
while (not q.empty() and l <= q.front() and q.front() <= r)
q.pop();
}
return q.empty();
}
ll binsearch() {
ll l = 0, r = 1e9 + 1;
while (l < r) {
ll mid = (l + r) / 2;
if (check(mid))
r = mid;
else
l = mid + 1;
}
if (l == ll(1e9 + 1))
return -1;
return l;
}
void program() {
input();
ll ans = binsearch();
cout << ans << "\n";
if (ans == -1)
return;
check(ans);
cout << str << "\n";
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
program();
return 0;
}
