#include<bits/stdc++.h>
using namespace std;
#define ll long long int
#define pb push_back
#define en cout << '\n'
#define vi vector<int>
#define pii pair<int, int>
#define ff first
#define ss second
#define all(x) x.begin(),x.end()
const int N = 1e5+100;
int n, m, a[N], b[N];
int dp[N][2], par[N][2];
int get(int l, int r){
if(r < l) return 0;
return upper_bound(b+1, b+1+m, r) - lower_bound(b+1, b+1+m, l);
}
int get_first(int l){
int pos = lower_bound(b+1, b+1+m, l) - b;
if(pos == m+1) return 2e9;
return b[pos];
}
void solve(){
cin >> n >> m;
vector<pii> v;
for(int i = 1; i <= n; ++i){
cin >> a[i];
v.pb({a[i], 1});
}
for(int i = 1; i <= m; ++i){
cin >> b[i];
v.pb({b[i], 0});
}
sort(all(v));
string soll;
int l = 0, r = 1e9+2, ans = -1;
while(l <= r){
int k = l+r>>1;
string sol = "";
bool ok = 1;
int last_covered = -2e9;
dp[1][0] = get(-2e9, a[1] - k - 1) > 0 ? b[1] : get_first(a[1] + 1);
dp[1][1] = get(-2e9, a[1] - 1) > 0 ? b[1] : get_first(a[1] + k + 1);
for(int i = 2; i <= n ;++i){
int L = a[i] - k, R = a[i];
if(dp[i - 1][0] >= L){
dp[i][0] = get_first(a[i] + 1);
par[i][0] = 0;
}else{
dp[i][0] = -2e9;
}
if(dp[i - 1][0] >= a[i]){
par[i][1] = 0;
dp[i][1] = get_first(a[i] + k + 1);
}else{
dp[i][1] = dp[i - 1][0];
par[i][1] = 0;
}
if(dp[i-1][1] >= L){
if(dp[i][0] < get_first(max(a[i - 1] + k + 1, a[i] + 1))){
par[i][0] = 1;
}
dp[i][0] = max(dp[i][0], get_first(max(a[i - 1] + k + 1, a[i] + 1)));
}else{
dp[i][0] = max(dp[i][0], (int)(-2e9));
}
if(dp[i-1][1] >= a[i]){
if(dp[i][1] < get_first(a[i] + k + 1)){
par[i][1] = 1;
}
dp[i][1] = max(dp[i][1], get_first(a[i] + k + 1));
}else{
if(dp[i][1] < dp[i - 1][1]){
dp[i][1] = dp[i - 1][1];
par[i][1] = 1;
}
}
}
if(max(dp[n][0], dp[n][1]) == (int)2e9){
ok = 1;
int x = 0;
if(dp[n][0] == 2e9) x = 0;
else x = 1;
sol += (x==0?'L':'R');
for(int i = n - 1; i >= 1; --i){
x = par[i + 1][x];
sol += (x==0?'L':'R');
}
reverse(all(sol));
}
else ok = 0;
// cout << k << '\n';
// for(int i = 1; i <= n; ++i) cout << dp[i][0] << ' ' << dp[i][1] << '\n';
if(ok){
ans = k;
soll = sol;
r = k - 1;
}else{
l = k + 1;
}
}
cout << ans << '\n';
if(ans != -1){
cout << soll;
}
}
int main(){
cin.tie(0); ios::sync_with_stdio(0);
solve();
return 0;
}
