#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
#define debug(x) cerr << '[' << (#x) << "] = " << x << '\n';
template<class T> using ordered_set = tree<T, null_type , less<T> , rb_tree_tag , tree_order_statistics_node_update> ;
void PlayGround() {
int N; cin >> N;
vector<int>a(N);
for(int i=0; i<N; ++i) cin >> a[i];
sort(a.begin(), a.end());
if(N < 4) {
cout << 1 << '\n' << a[0] << '\n' << N-1 << '\n';
for(int i=1; i<N; ++i) cout << a[i] << ' ';
cout << '\n';
return;
}
auto print = [] (vector<int>&x, vector<int>&y) {
if(y.empty()) y.push_back(x.back()), x.pop_back();
cout << x.size() << '\n';
for(auto it : x) cout << it << ' ';
cout << '\n';
cout << y.size() << '\n';
for(auto it : y) cout << it << ' ';
cout << "\n";
};
auto msTomp = [] (multiset<int>&ms, map<int,int>&mp) {
auto it = ms.begin();
auto it2 = it;
++it2;
while(it2!=ms.end()) {
mp[*it2-*it]++;
++it2, ++it;
}
};
auto insertNew = [] (multiset<int>::iterator it, multiset<int>&ms, map<int,int>&mp) {
if(it!=ms.begin() && next(it, 1)!=ms.end()) {
int gap = *next(it, 1) - *prev(it, 1);
mp[gap]--;
if(mp[gap]==0) mp.erase(gap);
mp[*it - *prev(it, 1)]++;
mp[*next(it, 1) - *it]++;
} else if(it!=ms.begin()) {
mp[*it-*prev(it, 1)]++;
} else if(next(it, 1)!=ms.end()) {
mp[*next(it, 1)-*it]++;
}
};
auto Process = [=] (vector<int>&x, int third=-1) {
multiset<int>ms;
map<int,int>mp;
vector<int>y;
int dif = x[1] - x[0];
if(third!=-1) ms.insert(a[third]);
for(int i=3; i<N; ++i) {
if(a[i]-x.back()==dif) x.push_back(a[i]);
else ms.insert(a[i]);
}
if(ms.empty()) {
print(x, y);
exit(0);
}
msTomp(ms, mp);
for(int i=x.size(); i>0; --i) {
if(i<x.size()) {
ms.insert(x[i]);
insertNew(ms.find(x[i]), ms, mp);
}
if(mp.size()<2) {
for(auto it : ms) y.push_back(it);
x.resize(i);
print(x, y);
exit(0);
}
}
};
vector<int>b = {0, 1, 2};
do {
vector<int>x = {a[b[0]], a[b[1]]};
if(x[0]>x[1]) swap(x[0], x[1]);
Process(x, b[2]);
} while(next_permutation(b.begin(), b.end()));
if(a[2]-a[1]!=a[1]-a[0]) {
cout << -1 << '\n';
return;
}
vector<int>x = {a[0], a[1], a[2]};
Process(x);
cout << -1 << '\n';
#ifndef ONLINE_JUDGE
cerr << "Time elapsed: " << 1.0 * clock() / CLOCKS_PER_SEC << " s.\n";
#endif
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
PlayGround();
return 0;
}
