#include <bits/stdc++.h>
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2")
#define int long long
#define pii pair<int,int>
#define vi vector<int>
#define ff first
#define ss second
#define sp << " " <<
#define all(x) x.begin(),x.end()
#define big(x) ((int)(x.size()))
using namespace std;
const int MOD = 1e9+7, LIM = 1e6+1, inf = 2e18;
const int N = 1e5+1;
void solve() {
int n,m;
cin >> n >> m;
vi s(n+1),f(m+1);
for (int i=1;i<=n;i++) cin >> s[i];
for (int i=1;i<=m;i++) cin >> f[i];
vector<char> direction(n+1,'R');
auto check =[&](int x) -> bool {
vi dp(n+1,0);
int ptr = 0,ptr2 = 0,ptr3 = 0;
for (int i=1;i<=n;i++) {
while (ptr<m && f[ptr+1] <= s[i]) ptr++;
while (ptr2<m && f[ptr2+1] <= s[i]+x) ptr2++;
while (i>1 && ptr3 < m && f[ptr3+1] <= s[i-1]+x) ptr3++;
dp[i] = dp[i-1];
if (f[dp[i-1]+1] < s[i]-x) return false;
//bunu sola düz
if (f[dp[i-1]+1] <= s[i]) {
if (ptr > dp[i]) {
dp[i] = ptr;
direction[i] = 'L';
}
}
if (f[dp[i-1]+1] >= s[i]) {
if (ptr2 > dp[i]) {
dp[i] = ptr2;
direction[i] = 'R';
}
}
if (i>1 && (s[i-1]+x >= s[i]-x) && (f[dp[i-2]+1] <= s[i] && f[dp[i-2]+1] >= s[i]-x)) {
if (ptr3 > dp[i]) {
dp[i] = ptr3;
direction[i] = 'L';
direction[i-1] = 'R';
}
}
if (dp[i] == m) {
for (int j = i+1;j<=n;j++) direction[j] = 'R';
return true;
}
}
return false;
};
int l = 0;
int r = inf;
while (l<=r) {
int mid = (l+r) >> 1;
if (check(mid)) r = mid-1;
else l = mid+1;
}
if (l < inf) {
cout << l << '\n';
check(l);
for (int i=1;i<=n;i++) cout << direction[i];
cout << '\n';
}
else cout << -1 << '\n';
}
signed main() {
ios_base::sync_with_stdio(0); cin.tie(0);
int t = 1;
//cin >> t;
while (t --> 0) solve();
}
