#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define ll long long
#define ld long double
#define ull unsigned long long
#define ff first
#define ss second
#define pii pair<int,int>
#define pll pair<long long, long long>
#define vi vector<int>
#define vl vector<long long>
#define pb push_back
#define rep(i, b) for(int i = 0; i < (b); ++i)
#define rep2(i,a,b) for(int i = a; i <= (b); ++i)
#define rep3(i,a,b,c) for(int i = a; i <= (b); i+=c)
#define count_bits(x) __builtin_popcountll((x))
#define all(x) (x).begin(),(x).end()
#define siz(x) (int)(x).size()
#define forall(it,x) for(auto& it:(x))
using namespace __gnu_pbds;
using namespace std;
typedef tree<int, null_type, less<int>, rb_tree_tag,tree_order_statistics_node_update> ordered_set;
//mt19937 mt;void random_start(){mt.seed(chrono::time_point_cast<chrono::milliseconds>(chrono::high_resolution_clock::now()).time_since_epoch().count());}
//ll los(ll a, ll b) {return a + (mt() % (b-a+1));}
const int INF = 1e9+50;
const ll INF_L = 1e18+40;
const ll MOD = 1e9+7;
vl spri;
vl flow;
pii dp[100'001][2];
int next_flow(ll poz)
{
int p = 0;
int k = siz(flow)-1;
int ans = siz(flow);
while(p <= k)
{
int mid = (p+k)/2;
if(flow[mid] > poz)
{
ans = mid;
k = mid-1;
}
else
{
p = mid+1;
}
}
return ans;
}
bool solve(ll k)
{
int n = siz(spri)-1;
int m = siz(flow);
rep2(i,1,n)
{
dp[i][0] = {-1,-1};
dp[i][1] = {-1,-1};
}
rep2(i,1,n)
{
dp[i][0] = {0,-1};
dp[i][1] = {0,-1};
// left left
if(spri[i] - flow[dp[i-1][0].ff] <= k)
{
dp[i][0] = max(dp[i][0],{next_flow(spri[i]),0});
}
// left right
if(spri[i] - flow[dp[i-1][1].ff] <= k && i != 1)
{
dp[i][0] = max(dp[i][0],{next_flow(max(spri[i],spri[i-1]+k)),1});
}
// right left
if(flow[dp[i-1][0].ff] >= spri[i])
{
dp[i][1] = max(dp[i][1],{next_flow(spri[i]+k),0});
}
else
{
dp[i][1] = max(dp[i][1],{dp[i-1][0].ff,0});
}
//right right
if(flow[dp[i-1][1].ff] >= spri[i])
{
dp[i][1] = max(dp[i][1],{next_flow(spri[i]+k),1});
}
else
{
dp[i][1] = max(dp[i][1],{dp[i-1][1].ff,1});
}
// cout << dp[i][0] << " " << dp[i][1] << " " << i << " " << n << " " << m << " dp\n";
if(dp[i][0].ff == m) return true;
if(dp[i][1].ff == m) return true;
}
return false;
}
int main()
{
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
//random_start();
spri.pb(-1);
int n,m;
cin >> n >> m;
rep(i,n)
{
int x;
cin >> x;
spri.pb(x);
}
rep(i,m)
{
int x;
cin >> x;
flow.pb(x);
}
int p = 0;
int k = 1e9;
int ans = -1;
while(p <= k)
{
int mid = (p+k)/2;
if(solve(mid))
{
ans = mid;
k = mid-1;
}
else
{
p = mid+1;
}
}
cout << ans << "\n";
if(ans == -1) return 0;
vector<bool> vans(n,0);
int cur_done = m;
solve(ans);
// cout << next_flow(10) << " nxt\n";
// rep2(i,1,n)
// {
// cout << dp[i][0].ff << " " << dp[i][1].ff << "\n";
// }
int cur_ = 0;
for(int i = n; i >= 1; i--)
{
if(dp[i][0].ff == -1) continue;
if(dp[i][0].ff == m)
{
cur_ = dp[i][0].ss;
continue;
}
else if(dp[i][1].ff == m)
{
cur_ = dp[i][1].ss;
vans[i] = 1;
continue;
}
vans[i] = cur_;
cur_ = dp[i][cur_].ss;
}
rep(i,n)
{
if(vans[i] == 0) cout << "L";
else cout << "R";
}
}
