#include<bits/stdc++.h>
using namespace std;
#define int long long
#define inf (int)2e18
#define nl '\n'
void solve(){
int n, m;
cin>>n>>m;
int s[n+4];
s[0] = s[1] = s[2] = -inf;
for(int i = 3; i < n+3; i++) cin>>s[i];
s[n+3] = inf;
int f[m+1];
f[0] = -inf;
for(int i = 1; i <= m; i++) cin>>f[i];
int dp[n+4][3];
pair<int,int> rec[n+4][3];
int k;
for(int i : {0, 1, 2}){
dp[i][0] = dp[i][1] = 0;
dp[i][2] = 1;
}
auto get = [&](int x){
int i = lower_bound(f+1, f+m+1, x) - f - 1;
return f[i];
};
auto set = [&](int i, int x, int fi, int fj){
int p = get(x);
auto &d = dp[fi][fj];
auto &r = rec[fi][fj];
if(dp[i][0] and p <= s[i] + k){ // R
d = 1;
r = {i, 0};
}
else if(dp[i][1] and p <= s[i-1] + k){ // RL
d = 1;
r = {i, 1};
}
else if(dp[i][2] and p <= s[i]){ // L
d = 1;
r = {i, 2};
}
};
auto check = [&]{
for(int i = 3; i <= n+3; i++){
dp[i][0] = dp[i][1] = dp[i][2] = 0;
// R
set(i-1, s[i], i, 0);
// RL
if(get(s[i] - k) <= s[i-1] + k){
set(i-2, min(s[i-1], s[i] - k), i, 1);
}
// L
set(i-1, s[i] - k, i, 2);
}
return dp[n+3][0];
};
int lo = 0, hi = 1e9;
while(lo < hi){
k = (lo + hi)/2;
if(check()) hi = k;
else lo = k+1;
}
k = lo;
if(!check()){
cout<<-1<<nl;
return;
}
string ans;
int i = n+3, j = 0;
while(i >= 3){
auto [pi, pj] = rec[i][j];
if(j == 0) ans += "R";
if(j == 1) ans += "LR";
if(j == 2) ans += "L";
i = pi;
j = pj;
}
reverse(ans.begin(), ans.end());
ans.pop_back();
cout<<lo<<nl<<ans;
}
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(NULL);cout.tie(NULL);
int t = 1;
//cin>>t;
while(t--) solve();
return 0;
}
