#include <bits/stdc++.h>
using namespace std;
using P = pair<int,int>;
const int N=1e5+5;
const int INF=INT_MAX/2;
int n,m;
int s[N],f[N];
pair<int,int> dp[N][2];
bool check(int x){
int a=1,b=1,c=1;
dp[0][0]=dp[0][1]={1,0};
for(int i=1;i<=n;i++){
while(a<=m&&f[a]<=s[i])a++;
while(b<=m&&f[b]<=s[i-1]+x)b++;
while(c<=m&&f[c]<=s[i]+x)c++;
dp[i][0]=dp[i][1]=max(P(dp[i-1][0].first,0),P(dp[i-1][1].first,1));
if(f[dp[i-1][0].first]>=s[i]-x)dp[i][0]=max(dp[i][0],P(a,0));
if(f[dp[i-1][1].first]>=s[i]-x)dp[i][0]=max(dp[i][0],P(max(a,b),1));
if(f[dp[i-1][0].first]>=s[i])dp[i][1]=max(dp[i][1],P(c,0));
if(f[dp[i-1][1].first]>=s[i])dp[i][1]=max(dp[i][1],P(c,1));
}
return max(dp[n][0],dp[n][1]).first>m;
}
int main(){
cin.tie(nullptr)->sync_with_stdio(false);
cin >> n >> m;
for(int i=1;i<=n;i++)cin >> s[i];
for(int i=1;i<=m;i++)cin >> f[i];
s[0]=-INF;
f[m+1]=INF;
int l=0,r=INF;
while(l<r){
int md=(l+r)/2;
if(check(md))r=md;
else l=md+1;
}
if(l==INF)cout << -1 << "\n";
else{
check(l);
string ans(n,' ');
for(int i=n,j=dp[n][1]>dp[n][0];i>=1;i--){
ans[i-1]="LR"[j];
j=dp[i][j].second;
}
cout << l << "\n";
cout << ans << "\n";
}
}
