#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
#define ff first
#define ss second
#define pb push_back
#define all(a) (a).begin(), (a).end()
#define replr(i, a, b) for (int i = int(a); i <= int(b); ++i)
#define reprl(i, a, b) for (int i = int(a); i >= int(b); --i)
#define rep(i, n) for (int i = 0; i < int(n); ++i)
#define mkp(a, b) make_pair(a, b)
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> PII;
typedef vector<int> VI;
typedef vector<PII> VPI;
typedef vector<VI> VVI;
typedef vector<VVI> VVVI;
typedef vector<VPI> VVPI;
typedef pair<ll, ll> PLL;
typedef vector<ll> VL;
typedef vector<PLL> VPL;
typedef vector<VL> VVL;
typedef vector<VVL> VVVL;
typedef vector<VPL> VVPL;
template<class T> T setmax(T& a, T b) {if (a < b) return a = b; return a;}
template<class T> T setmin(T& a, T b) {if (a < b) return a; return a = b;}
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
template<class T>
using indset = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
typedef vector<char> VC;
typedef vector<VC> VVC;
typedef vector<bool> VB;
typedef vector<VB> VVB;
void solve() {
int n, m;
cin >> n >> m;
VI a(n);
for (int& x : a) cin >> x;
VI b(m);
for (int& x : b) cin >> x;
auto expand = [&](int last, int L, int R) {
if (last == m) return m;
if (b[last] < L) return -1;
while (last != m && b[last] <= R) last++;
return last;
};
string ans(n, '_');
auto can = [&](int d) {
VI dp(n+1, -1);
VI cs(n+1);
dp[0] = 0;
replr(i, 1, n) {
int case1 = expand(dp[i-1], a[i-1]-d, a[i-1]);
int case2 = expand(dp[i-1], a[i-1], a[i-1]+d);
int case3 = -1;
if (i != 1 && a[i-2] - a[i-1] <= d) {
case3 = expand(dp[i-2], a[i-1]-d, a[i-2]+d);
}
if (case1 > dp[i]) {
dp[i] = case1;
cs[i] = 1;
}
if (case2 > dp[i]) {
dp[i] = case2;
cs[i] = 2;
}
if (case3 > dp[i]) {
dp[i] = case3;
cs[i] = 3;
}
if (dp[i] == -1) return false;
}
int cur = n;
while (cur) {
if (cs[cur] == 1) {
ans[--cur] = 'L';
} else if (cs[cur] == 2) {
ans[--cur] = 'R';
} else if (cs[cur] == 3) {
ans[--cur] = 'L';
ans[--cur] = 'R';
}
}
return dp[n] == m;
};
int l = -1, r = 1e9;
while (l+1 < r) {
int m = (l + r) / 2;
if (can(m)) r = m;
else l = m;
}
if (can(r)) {
cout << r << endl;
cout << ans << endl;
} else {
cout << -1 << endl;
}
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL), cout.tie(NULL);
/*freopen("mincross.in", "r", stdin); */
/*freopen("test.out", "w", stdout); */
int t = 1;
/*cin >> t; */
while (t--) solve();
}
