#include <bits/stdc++.h>
#define F(i,x,y) for(int i=(x);i<=(y);i++)
#define DF(i,x,y) for(int i=(x);i>=(y);i--)
#define ms(x,y) memset(x,y,sizeof(x))
#define SZ(x) (int)x.size()-1
#define all(x) x.begin(),x.end()
#define pb push_back
using namespace std;
typedef long long LL;
typedef unsigned long long ull;
typedef pair<int,int> pii;
template<typename T> void chkmax(T &x,T y){ x=max(x,y);}
template<typename T> void chkmin(T &x,T y){ x=min(x,y);}
template<typename T> void read(T &FF){
    FF=0;int RR=1;char ch=getchar();
    for(;!isdigit(ch);ch=getchar()) if(ch=='-') RR=-1;
    for(;isdigit(ch);ch=getchar()) FF=(FF<<1)+(FF<<3)+ch-48;
    FF*=RR;
}
const int N=100010;
int n,m,a[N],b[N];
bool dir[N];
bool chk(int mid){
    int j=m;
    DF(i,n,1){
        if(b[j]>a[i]){
            if(b[j]>a[i]+mid) return 0;
            dir[i]=1;
            while(j&&b[j]>=a[i]) j--;
        }
        else{
            dir[i]=0;
            while(j&&b[j]>=a[i]-mid) j--;
        }
        if(!j) return 1;
    }
    return 0;
}
int main(){
    read(n),read(m);
    F(i,1,n) read(a[i]);
    F(i,1,m) read(b[i]);
    int lo=-1,hi=1e9+5;
    while(lo<hi-1){
        int mid=(lo+hi)>>1;
        if(chk(mid)) hi=mid;
        else lo=mid;
    }
    if(hi==1e9+5){ puts("-1");exit(0);}
    chk(hi);
    printf("%d\n",hi);
    F(i,1,n) if(dir[i]) putchar('R');else putchar('L');puts("");
    return 0;
}