#include <bits/stdc++.h>
using namespace std;
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
int n, m;
cin >> n >> m;
vector<int> s(n);
for (int i = 0; i < n; i++) {
cin >> s[i];
}
vector<int> f(m);
for (int i = 0; i < m; i++) {
cin >> f[i];
}
auto Check = [&](int k) {
vector<int> dp(n + 1, -1);
for (int i = 0; i < n; i++) {
if (dp[i] == m - 1) {
break;
}
if (i + 1 < n) {
// take anything
dp[i + 1] = max(dp[i + 1], dp[i]);
}
if (f[dp[i] + 1] >= s[i] - k && f[dp[i] + 1] <= s[i]) {
// L
int from = (int) (lower_bound(f.begin(), f.end(), s[i] - k) - f.begin());
int to = (int) (lower_bound(f.begin(), f.end(), s[i] + 1) - f.begin()) - 1;
dp[i + 1] = max(dp[i + 1], to);
}
if (f[dp[i] + 1] >= s[i] && f[dp[i] + 1] <= s[i] + k) {
// R
int from = (int) (lower_bound(f.begin(), f.end(), s[i]) - f.begin());
int to = (int) (lower_bound(f.begin(), f.end(), s[i] + k + 1) - f.begin()) - 1;
dp[i + 1] = max(dp[i + 1], to);
}
if (i + 1 < n && f[dp[i] + 1] >= s[i + 1] - k && f[dp[i] + 1] <= s[i + 1]) {
// RL
int from = (int) (lower_bound(f.begin(), f.end(), s[i + 1] - k) - f.begin());
int to = (int) (lower_bound(f.begin(), f.end(), s[i + 1] + 1) - f.begin()) - 1;
if (to == m - 1) {
dp[i + 2] = max(dp[i + 2], m - 1);
continue;
}
if (f[to + 1] >= s[i] && f[to + 1] <= s[i] + k) {
to = (int) (lower_bound(f.begin(), f.end(), s[i] + k + 1) - f.begin()) - 1;
dp[i + 2] = max(dp[i + 2], to);
}
}
}
return *max_element(dp.begin(), dp.end()) == m - 1;
};
int low = 0, high = 1e9, k = -1;
while (low <= high) {
int mid = (low + high) >> 1;
if (Check(mid)) {
k = mid;
high = mid - 1;
} else {
low = mid + 1;
}
}
if (k == -1) {
cout << k << '\n';
return 0;
}
vector<int> dp(n + 1, -1);
vector<int> d(n + 1);
auto Update = [&](int p, int v, int t) {
if (dp[p] < v) {
dp[p] = v;
d[p] = t;
}
};
for (int i = 0; i < n; i++) {
if (dp[i] == m - 1) {
Update(i + 1, dp[i], 0);
continue;
}
if (i + 1 < n) {
// take anything
Update(i + 1, dp[i], 0);
}
if (f[dp[i] + 1] >= s[i] - k && f[dp[i] + 1] <= s[i]) {
// L
int from = (int) (lower_bound(f.begin(), f.end(), s[i] - k) - f.begin());
int to = (int) (lower_bound(f.begin(), f.end(), s[i] + 1) - f.begin()) - 1;
Update(i + 1, to, 0);
}
if (f[dp[i] + 1] >= s[i] && f[dp[i] + 1] <= s[i] + k) {
// R
int from = (int) (lower_bound(f.begin(), f.end(), s[i]) - f.begin());
int to = (int) (lower_bound(f.begin(), f.end(), s[i] + k + 1) - f.begin()) - 1;
Update(i + 1, to, 1);
}
if (i + 1 < n && f[dp[i] + 1] >= s[i + 1] - k && f[dp[i] + 1] <= s[i + 1]) {
// RL
int from = (int) (lower_bound(f.begin(), f.end(), s[i + 1] - k) - f.begin());
int to = (int) (lower_bound(f.begin(), f.end(), s[i + 1] + 1) - f.begin()) - 1;
if (to == m - 1) {
Update(i + 2, m - 1, 2);
continue;
}
if (f[to + 1] >= s[i] && f[to + 1] <= s[i] + k) {
to = (int) (lower_bound(f.begin(), f.end(), s[i] + k + 1) - f.begin()) - 1;
Update(i + 2, to, 2);
}
}
}
vector<char> dir(n);
int p = n;
while (p > 0) {
if (d[p] == 0) {
--p;
dir[p] = 'L';
} else if (d[p] == 1) {
--p;
dir[p] = 'R';
} else {
--p;
dir[p] = 'L';
--p;
dir[p] = 'R';
}
}
cout << k << '\n';
for (int i = 0; i < n; i++) {
cout << dir[i];
}
return 0;
}
