#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <string>
#include <algorithm>
#include <cstring>
#include <cstdio>
#include <sstream>
#include <map>
#include <stack>
#include <set>
#include <queue>
#include <list>
#include <unordered_set>
#include <unordered_map>
#include <math.h>
#include <bitset>
#include <cmath>
#include <vector>
#include <iomanip>
#include <random>
#include <chrono>
#include <cassert>
using namespace std;
#define ll long long
#define fr first
#define sc second
#define pb push_back
#define US freopen(".in", "r", stdin); freopen("j.out", "w", stdout);
ll gcd(ll a, ll b)
{
if (a == 0 || b == 0) {
return max(a, b);
}
if (a <= b) {
return gcd(a, b % a);
}
else {
return gcd(a % b, b);
}
}
ll lcm(ll a, ll b) {
return (a / gcd(a, b)) * b;
}
const int N = 200005;
const ll oo = 100000000000000000, MOD = 1000000007;
ll s[N], f[N], dp[N];
int n, m;
char pat[N], ans[N];
int func(int ind, ll l, ll r) {
while (f[ind] >= l && f[ind] <= r && ind<=m) {
++ind;
}
--ind;
return ind;
}
int func1(int ind, ll l, ll r,ll l1,ll r1) {
while (ind<=m) {
if ((f[ind] >= l && f[ind] <= r) || (f[ind] >= l1 && f[ind] <= r1)) {
++ind;
}
else {
break;
}
}
--ind;
return ind;
}
bool from[N][5];
void solve() {
cin >> n >> m;
for (int i = 1; i <= n; ++i) {
cin >> s[i];
}
for (int i = 1; i <= m; ++i) {
cin >> f[i];
}
ll l = 0, r = 10000000000, anss = oo;
while (l <= r) {
ll mid = (l + r) / 2;
dp[0] = 0;
for (int i = 1; i <= n; ++i) {
dp[i] = 0;
for (int j = 0; j < 3; ++j) {
from[i][j] = 0;
}
}
for (int i = 0; i <= n-1; ++i) {
int ind = dp[i];
++ind;
ind = func(ind, s[i+1] - mid, s[i+1]);
if (ind > dp[i + 1]) {
dp[i + 1] = ind;
for (int j = 0; j < 3; ++j) {
from[i + 1][j] = 0;
}
from[i + 1][0] = 1;
ans[i + 1] = 'L';
}
ind = dp[i];
++ind;
ind = func(ind, s[i+1], s[i+1] + mid);
if (ind > dp[i + 1]) {
dp[i + 1] = ind;
for (int j = 0; j < 3; ++j) {
from[i + 1][j] = 0;
}
from[i + 1][1] = 1;
ans[i + 1] = 'R';
}
ind = dp[i] + 1;
ind = func1(ind, s[i+1], s[i+1] + mid, s[i + 2] - mid, s[i + 2]);
if (ind > dp[i + 2]) {
for (int j = 0; j < 3; ++j) {
from[i + 2][j] = 0;
}
from[i + 2][2] = 1;
ans[i + 1] = 'R';
dp[i + 2] = ind;
ans[i + 2] = 'L';
}
}
if (dp[n] == m) {
for (int i = n; i >= 1; --i) {
if (from[i][0] == 1) {
pat[i] = 'L';
}
else {
if (from[i][1] == 1) {
pat[i] = 'R';
}
else {
pat[i] = 'L';
pat[i - 1] = 'R';
--i;
}
}
}
anss = min(anss, mid);
r = mid - 1;
}
else {
l = mid + 1;
}
}
if (anss == oo) {
cout << -1 << endl;
return;
}
cout << anss << endl;
for (int i = 1; i <= n; ++i) {
cout << pat[i];
}
}
int main() {
ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
//US
int tt = 1;
//cin >> tt;
while (tt--) {
solve();
}
}
