#include <bits/stdc++.h>
#define F first
#define S second
using namespace std;
using ll = long long;
using pi = pair<int, int>;
using vi = vector<int>;
template<class T> bool ckmin(T& a, T b) { return b < a ? a = b, true : false; }
template<class T> bool ckmax(T& a, T b) { return a < b ? a = b, true : false; }
const int N = 1e5 + 7;
int n, m, a[N], b[N], p[N], dp[N];
bool check(int d) {
int j = 1, k = 1, l = 1;
for (int i = 1; i <= n; ++i) {
if (b[dp[i - 1] + 1] < a[i] - d) return false;
while (j <= m && b[j] <= a[i] + d) ++j;
while (k <= m && b[k] <= a[i]) ++k;
if (i > 1) {
while (l <= m && b[l] <= a[i - 1] + d) ++l;
}
if (b[dp[i - 1] + 1] >= a[i]) {
dp[i] = j - 1;
p[i] = 1;
} else {
dp[i] = k - 1;
p[i] = 0;
}
if (i > 1 && b[dp[i - 2] + 1] >= a[i] - d && dp[i] < l) {
dp[i] = l - 1;
p[i] = -1;
}
}
return dp[n] == m;
}
int main() {
ios::sync_with_stdio(0); cin.tie(0);
cin >> n >> m;
for (int i = 1; i <= n; ++i) cin >> a[i];
for (int i = 1; i <= m; ++i) cin >> b[i];
b[m + 1] = 2e9 + 10;
int low = 0, high = 1e9, sol = -1;
while (low <= high) {
int mid = (low + high) / 2;
if (check(mid)) {
sol = mid;
high = mid - 1;
} else {
low = mid + 1;
}
}
check(sol);
cout << sol << "\n";
if (sol == -1) return 0;
vector<char> s(n + 1);
for (int i = n; i >= 1; --i) {
if (p[i] == -1) {
s[i] = 'L';
s[i - 1] = 'R';
--i;
} else {
s[i] = (p[i] == 0 ? 'L' : 'R');
}
}
for (int i = 1; i <= n; ++i) cout << s[i];
}
