#include <bits/stdc++.h>
#define int long long
using namespace std;
const int N=100010, INF=1e9;
int n, m, ans=-1, a[N], b[N], dp[N];
pair<int, int> prv[N];
string ans2, tmp;
bool chk(int x) {
fill(dp+1, dp+n+2, INF);
for(int i=1; i<=n+1; i++) prv[i]={0, 0};
int t=1, s=1;
tmp.clear();
for(int i=1; i<=m; i++) tmp+="L";
dp[1]=1;
for(int i=1; i<=n; i++) {
while(dp[i]<=m && b[dp[i]]<a[i]-x) dp[i]++;
if(dp[i]>m) continue;
if(b[dp[i]]<=a[i]) {
int r=upper_bound(a+1, a+n+1, b[dp[i]]+x)-a;
if(dp[r]>dp[i]+1) dp[r]=dp[i]+1, prv[r]={i, 3};
continue;
}
int p=upper_bound(a+1, a+n+1, b[dp[i]])-a;
if(b[dp[i]]<=a[i]+x && dp[p]>dp[i]+1) dp[p]=dp[i]+1, prv[p]={i, 1};
if(dp[i]<m && b[dp[i]+1]<=a[i]+x) {
int q=upper_bound(a+1, a+n+1, b[dp[i]+1]+x)-a;
if(dp[q]>dp[i]+2) dp[q]=dp[i]+2, prv[q]={i, 2};
}
}
if(dp[n+1]>m+1) return false;
for(int i=prv[n+1].first, j=prv[n+1].second; i; j=prv[i].second, i=prv[i].first) {
if(j==1) tmp[dp[i]-1]='L';
if(j==2) tmp[dp[i]-1]='R', tmp[dp[i]]='L';
if(j==3) tmp[dp[i]-1]='R';
}
return true;
}
signed main() {
ios_base::sync_with_stdio(0); cin.tie(0);
cin>>m>>n;
for(int i=1; i<=m; i++) cin>>b[i];
for(int i=1; i<=n; i++) cin>>a[i];
for(int s=0, e=INF; s<=e; ) {
int m=(s+e)/2;
if(chk(m)) ans2=tmp, ans=m, e=m-1;
else s=m+1;
}
assert(n==1 || ans>=0);
if(ans<0) cout<<-1;
else cout<<ans<<"\n"<<ans2;
return 0;
}
