#include <bits/stdc++.h>
#define endl '\n'
#define ld long double
#define pb push_back
#define pf push_front
#define mod 998244353
#define se second
#define fi first
#define all(ls) (ls).begin(),(ls).end()
#define int long long
using namespace std;
int n,m,works;
const int N=1e5+10;
int s[N],f[N],d[N],dp[N];
pair<int,int>nxt(int x){
return {lower_bound(f+1,f+n+1,x)-f,upper_bound(f+1,f+n+1,x)-f-1};
}
void work(int mid){
works=0;
for(int i=1;i<=n;i++)
dp[i]=0;
for(int i=1;i<=n;i++){
dp[i]=dp[i-1];
pair<int,int>a=nxt(s[i]-mid),b=nxt(s[i]),c=nxt(s[i]+mid);
if((dp[i-1]+1)>=a.fi and dp[i]<b.se){
d[i]=0;
dp[i]=b.se;
}
if((dp[i-1]+1)>=b.fi and dp[i]<c.se){
d[i]=1;
dp[i]=c.se;
}
if(i>1){
pair<int,int>D=nxt(s[i-1]+mid);
if((dp[i-2]+1)>=a.fi and dp[i]<D.se){
d[i]=0;
d[i-1]=1;
dp[i]=D.se;
}
}
}
works=(dp[n]==m);
}
void solve(){
cin>>n>>m;
for(int i=1;i<=n;i++)
cin>>s[i];
for(int i=1;i<=m;i++)
cin>>f[i];
int low=0,high=1e14;
while(low<=high){
int mid=(low+high)/2;
work(mid);
if(works)
high=mid-1;
else
low=mid+1;
}
if(low==(1e14+1))
low=-1;
cout<<low<<endl;
if(low!=-1){
work(low);
for(int i=1;i<=n;i++){
if(d[i]==0)
cout<<'L';
else
cout<<'R';
}
cout<<endl;
}
}
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int t=1;
// cin>>t;
for(int i=1;i<=t;i++){
// cout<<"Scenario #"<<i<<":"<<" ";
solve();
}
}
