#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define v vector
#define _ <<' '<<
#define print(x) cout<<#x<<": "<<(x)<<endl
int n,m;
v<int> a, b;
pair<bool, string> check(const int k) {
v<int> dp(n+1, -1);
v<string> prv(n+1, "");
for (int i=0; i<n; i++) {
if (i!=n-1) { // rl
int ptr=dp[i];
while (ptr!=m-1 && ((a[i+1]<=b[ptr+1] && b[ptr+1]<=a[i+1]+k)||(a[i+2]-k<=b[ptr+1] && b[ptr+1]<=a[i+2]))) ++ptr;
if (ptr>dp[i+2]) {
dp[i+2]=ptr;
prv[i+2]="LR";
}
}
int ptr=dp[i]; // l
while (ptr!=m-1 && a[i+1]-k<=b[ptr+1] && b[ptr+1]<=a[i+1]) ++ptr;
if (ptr>dp[i+1]) {
dp[i+1]=ptr;
prv[i+1]="L";
}
ptr=dp[i]; // r
while (ptr!=m-1 && a[i+1]<=b[ptr+1] && b[ptr+1]<=a[i+1]+k) ++ptr;
if (ptr>dp[i+1]) {
dp[i+1]=ptr;
prv[i+1]="R";
}
}
string ret="";
int cur=n;
while (cur) {
//print(cur);
if (prv[cur].empty()) {
ret+="L";
cur-=1;
} else {
ret+=prv[cur];
cur-=prv[cur].size();
}
}
//if (k==7) for (int i=0; i<n; i++) cout<<prv[i]<<" sep ";
//if (k==7) cout<<'\n';
reverse(ret.begin(), ret.end());
return {dp[n]==m-1, ret};
}
int main(){
cin>>n>>m;
a.resize(n+1);
b.resize(m);
for (int i=1; i<=n; i++) cin>>a[i];
for (int i=0; i<m; i++) cin>>b[i];
int lo=0, hi=1000000005, res=-1;
string out;
while (lo<=hi) {
const auto m=lo+(hi-lo>>1);
//print(m);
auto [rs, st]=check(m);
if (rs) {
res=m;
hi=m-1;
out=st;
} else lo=m+1;
}
cout<<res<<'\n';
if (res!=-1) cout<<out<<'\n';
}
