#include <bits/stdc++.h>
#define F first
#define S second
#define all(x) x.begin(), x.end()
#define pb push_back
#define FIO ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0)
using namespace std;
typedef long long ll;
typedef pair <ll, ll> pii;
const int N = 1e5 + 7;
int n, m;
int a[N], b[N], dp[N], gt[N];
string t[N];
void update(int x, int y, int val, string s) {
if (dp[y] < val) {
dp[y] = val;
gt[y] = x;
t[y] = s;
}
}
void check(int k) {
memset(dp, -1, sizeof dp);
dp[0] = 0;
for (int i = 0; i < n; i++) {
if (dp[i] == -1) continue;
if (b[dp[i]]+k >= a[i] && b[dp[i]] <= a[i]) update(i, i+1, upper_bound(b, b+m, a[i])-b, "L");
if (b[dp[i]] >= a[i] && a[i]+k >= b[dp[i]]) update(i, i+1, upper_bound(b, b+m, a[i]+k)-b, "R");
if (a[i]+k < b[dp[i]]) update(i, i+1, dp[i], "R");
if (i < n-1 && b[dp[i]] < a[i] && b[dp[i]]+k >= a[i+1]) update(i, i+2, upper_bound(b, b+m, a[i]+k)-b, "LR");
}
}
int main () {
FIO;
cin >> n >> m;
for (int i = 0; i < n; i++) cin >> a[i];
for (int i = 0; i < m; i++) cin >> b[i];
b[m] = 2e9 + 7;
if (n == 1 && a[0] > b[0] && a[n-1] < b[m-1]) {
cout << "-1\n";
return 0;
}
int lo = 0, hi = 1e9;
while (lo < hi) {
int mid = (lo + hi) / 2;
check(mid);
if (dp[n] == m) hi = mid;
else lo = mid+1;
}
cout << lo << "\n";
check(lo);
int x = n;
string s;
while (x) {
s += t[x];
x = gt[x];
}
reverse(all(s));
cout << s;
return 0;
}
