#include "bits/stdc++.h"
using namespace std;
int n;
int C[7];
vector<int> I[7];
int main()
{
cin >> n;
int tot = 0;
for (int i = 0; i < n; ++i)
{
int x;
cin >> x;
C[x] ++;
I[x].push_back(i);
tot += x;
}
for (int c1 = 0; c1 <= C[1]; ++c1)
for (int c2 = 0; c2 <= C[2]; ++c2)
for (int c3 = 0; c3 <= C[3]; ++c3)
for (int c4 = 0; c4 <= C[4]; ++c4)
{
int sum = c1*1 + c2*2 + c3*3 + c4*4;
if (sum*2 == tot)
{
vector<int> R;
for (int i = 0; i < c1; ++i) R.push_back(I[1][i]);
for (int i = 0; i < c2; ++i) R.push_back(I[2][i]);
for (int i = 0; i < c3; ++i) R.push_back(I[3][i]);
for (int i = 0; i < c4; ++i) R.push_back(I[4][i]);
cout << R.size() << endl;
sort(R.begin(), R.end());
for (int i = 0; i < R.size(); ++i)
{
if (i) cout << ' ';
cout << R[i]+1;
}
exit(0);
}
}
cout << -1 << endl;
}
