// Author: Robert Jaworski
#include <bits/stdc++.h>
using namespace std;
constexpr int DP_RANGE = 3;
constexpr int DP_SIZE = 1 << (2 * DP_RANGE);
void dp(int N, int M, const vector<int>& s, const vector<int>& f) {
vector<int> dir(N, -1);
int K = 0;
vector<int> dp(DP_SIZE + M*DP_SIZE, -1);
auto DP = [&] (int fi, int conf) -> int& {
return dp[DP_SIZE + fi * DP_SIZE + conf];
};
auto COVER = [&] (int fi, int si, int conf) {
int k = 0x7fffffff;
if (si >= 0 && s[si] == f[fi]) return 0;
for (int j = 0; j < DP_RANGE; j++) {
int i = si-DP_RANGE+1 + j;
if (i >= 0 && (conf & (1 << j)) != 0) {
k = min(k, f[fi] - s[i]);
}
}
for (int j = DP_RANGE; j < 2*DP_RANGE; j++) {
int i = si-DP_RANGE+1 + j;
if (i < N && (conf & (1 << j)) == 0) {
k = min(k, s[i] - f[fi]);
}
}
return k;
};
auto DO_COVER = [&] (int fi, int si, int conf) {
for (int j = 0; j < 2*DP_RANGE; j++) {
int i = si-DP_RANGE+1 + j;
if (0 <= i && i < N) {
if (dir[i] != -1 && (dir[i] == 0) != ((conf & (1 << j)) == 0)) {
cerr << "Bad cover " << i << " " << s[i] << endl;
}
dir[i] = conf & (1 << j);
}
}
};
auto PREV = [&] (int fi, int ds, int conf) {
if (!ds) return DP(fi-1, conf);
int k = 0x7fffffff;
for (int c = 0; c < DP_SIZE; c++) {
if (ds > 2*DP_RANGE || (c >> ds) == (conf & ((DP_SIZE-1) >> ds))) {
k = min(k, DP(fi-1, c));
}
}
return k;
};
for (int fi = 0, si = -1, psi = -1; fi < M; fi++) {
while (si + 1 < N && s[si+1] <= f[fi]) si++;
for (int conf = 0; conf < DP_SIZE; conf++) {
DP(fi, conf) = COVER(fi, si, conf);
DP(fi, conf) = max(DP(fi, conf), PREV(fi, si - psi, conf));
}
psi = si;
}
for (int fi = M, si = N-1, c=0, cm=0; fi-- > 0;) {
while (si >= 0 && s[si] > f[fi]) {
si--;
c <<= 1;
cm &= cm - 1;
}
int minK = 0x7fffffff, minC = 0;
for (int conf = 0; conf < DP_SIZE; conf++) {
if ((conf & cm) == (c & cm)) {
if (DP(fi, conf) < minK) {
minK = DP(fi, conf);
minC = conf;
}
}
}
DO_COVER(fi, si, minC);
c = minC;
cm = DP_SIZE-1;
K = max(K, minK);
}
if (K == 0x7fffffff) {
cout << -1 << endl;
return;
}
cout << K << endl;
for (auto&& x : dir) {
cout << (x ? 'R' : 'L');
}
cout << endl;
}
int main() {
int N, M;
cin >> N >> M;
vector<int> s(N, 0), f(M, 0);
for (auto&& x : s) {
cin >> x;
}
for (auto&& x : f) {
cin >> x;
}
dp(N, M, s, f);
return 0;
}
