#include <bits/stdc++.h>
using namespace std;
const int nx=1e5+5, mx=1e9+5, kx=10, bx=3;
int n, m, s[nx], f[nx], dr[nx], rv[nx][kx], l=0, r=1e9+5;
pair<int, int> dp[nx][kx];
bool solve(int x)
{
for (int i=1; i<=n; i++) dr[i]=0;
vector<int> vs(n+1), p, w;
vector<pair<int, int>> range;
p.push_back(0);
for (int i=4; i<=n; i++)
{
if (!range.empty()&&range.back().second>=s[i]-1) vs[i]=1, range.back().second=s[i]+x;
else if (s[i]-s[i-3]<=x) dr[i-3]=dr[i-1]=1, vs[i-3]=vs[i-2]=vs[i-1]=vs[i]=1, range.push_back({s[i-3]-x, s[i]+x});
}
for (int i=1; i<=n; i++) if (!vs[i]) p.push_back(i);
int idx=0;
for (int i=1; i<=m; i++)
{
while (idx<range.size()&&f[i]>range[idx].second) idx++;
if (range.empty()||f[i]<range[idx].first||f[i]>range[idx].second) w.push_back(i);
}
w.push_back(m+1);
vector<int> nxt(p.size()), nxtl(p.size());
idx=0;
for (int i=0; i<p.size(); i++)
{
while (f[w[idx]]<=s[p[i]]) idx++;
nxt[i]=idx;
}
idx=0;
for (int i=0; i<p.size(); i++)
{
while (f[w[idx]]<=s[p[i]]+x) idx++;
nxtl[i]=idx;
}
if (p.size()==1) return (w.size()==1);
for (int i=0; i<(1<<bx); i++) dp[0][i]={0, 0};
for (int i=1; i<p.size(); i++)
{
for (int msk=0; msk<(1<<bx); msk++)
{
int a=msk/2, b=msk/2+(1<<(bx-1));
if (dp[i-1][a].first<dp[i-1][b].first) swap(a, b);
int loc=f[w[dp[i-1][a].first]];
rv[i][msk]=a;
if (msk&1)
{
if (loc>=s[p[i]]-x&&loc<=s[p[i]]) dp[i][msk]={max(dp[i-1][a].second, nxt[i]), max(dp[i-1][a].second, nxt[i])};
else dp[i][msk]=dp[i-1][a];
}
else
{
if (loc>=s[p[i]]) dp[i][msk]={nxtl[i], nxtl[i]};
else dp[i][msk]={dp[i-1][a].first, nxtl[i]};
}
}
}
for (int i=0; i<(1<<bx); i++)
{
if (dp[p.size()-1][i].first==w.size()-1)
{
int cur=i;
for (int j=p.size()-1; j>0; j--) dr[p[j]]=cur%2, cur=rv[j][cur];
return 1;
}
}
return 0;
}
int main()
{
cin.tie(NULL)->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]=-2e9;
f[m+1]=INT_MAX;
while (l<r)
{
int md=(l+r)/2;
if (solve(md)) r=md;
else l=md+1;
}
if (l==mx) return cout<<-1, 0;
solve(l);
cout<<l<<'\n';
for (int i=1; i<=n; i++) cout<<(dr[i]?'L':'R');
}
