#include <bits/stdc++.h>
using namespace std;
#define int long long
#define rep(i,a,b) for(int i=a;i<=b;++i)
#define per(i,a,b) for(int i=a;i>=b;--i)
#define pb push_back
#define fi first
#define se second
const int MAXN = 1e5 + 10;
const int INF = 1e18+10;
int a[MAXN], dif[MAXN], n;
void check(int x, int y) {
multiset<int> s, dif;
int k = y-x;
rep(i,1,n) s.insert(a[i]);
s.erase(s.find(x));
s.erase(s.find(y));
vector<int> ans;
ans.pb(x); ans.pb(y);
int last = -1;
for (auto &v : s) {
if (last != -1) dif.insert(v-last);
last = v;
}
int tmp = y + k;
while ((int)ans.size() < n) {
if (*dif.begin() == *dif.rbegin()) {
cout << ans.size() << '\n';
for (int &v : ans) cout << v << " ";
cout << '\n' << s.size() << '\n';
for (auto &v : s) cout << v << " ";
cout << '\n';
exit(0);
}
auto it = s.find(tmp);
if (it == s.end()) break;
auto l = it, r = it;
if (it != s.begin()) {
l--;
dif.erase(dif.find(*it-*l));
}
if (++r != s.end()) {
dif.erase(dif.find(*r-*it));
if (it != s.begin()) dif.insert(*r-*l);
}
s.erase(it);
ans.pb(tmp);
tmp += k;
}
}
int32_t main(){
ios::sync_with_stdio(0);cin.tie(0);
cin >> n;
rep(i,1,n) cin >> a[i];
sort(a+1, a+n+1);
if (n==2) {
cout << "1\n" << a[1] << '\n' << "2\n" << a[2] << '\n';
return 0;
}
if (n <= 4) {
cout << "2\n";
rep(i,1,2) cout << a[i] << " \n"[i==2];
cout << n-2 << '\n';
rep(i,3,n) cout << a[i] << " \n"[i==n];
return 0;
}
check(a[1], a[2]);
check(a[1], a[3]);
check(a[2], a[3]);
cout << "-1\n";
return 0;
}
