#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define all(x) (x).begin(), (x).end()
#define sz(x) (int)size(x)
constexpr ll inf = 1e9 + 10;
int main(){
cin.tie(0)->sync_with_stdio(false);
int n, m;
cin >> n >> m;
vector<ll> s(n), f(m);
for(ll& e : s) cin >> e;
for(ll& e : f) cin >> e;
auto check = [&](ll len) -> string {
vector<int> dp(n+1, -1);
dp[0] = 0;
vector<pair<int, string>> prv(n+1);
for(int i = 0; i < n; i++){
if(dp[i] == -1) return "";
ll nxtf = dp[i] < m ? f[dp[i]] : inf;
if(nxtf + len < s[i]) return "";
vector<tuple<int, int, string>> opts;
opts.emplace_back(i+1, upper_bound(all(f), s[i]) - f.begin(), "L");
if(nxtf >= s[i]) opts.emplace_back(i+1, upper_bound(all(f), s[i]+len) - f.begin(), "R");
if(i < n-1 && s[i+1]-len <= nxtf) opts.emplace_back(i+2, upper_bound(all(f), s[i]+len) - f.begin(), "RL");
for(auto [i2, x, str] : opts){
if(dp[i2] < x){
dp[i2] = x;
prv[i2] = {i, str};
}
}
}
if(dp[n] < m) return "";
int i = n;
string rec;
while(i > 0){
auto [i2, str] = prv[i];
reverse(all(str));
rec += str;
i = i2;
}
reverse(all(rec));
return rec;
};
ll lo = -1, hi = inf;
while(lo+1 < hi){
ll mid = (lo + hi) / 2;
if(check(mid) == "") lo = mid;
else hi = mid;
}
if(hi == inf) cout << "-1\n";
else{
cout << hi << "\n";
cout << check(hi) << "\n";
}
}
