#include <bits/stdc++.h>
#ifdef LOCAL
#include "algorithmic-library/tools/debug.h"
#else
#define debug(...) (void)0
#define debug_if(...) (void)0
#endif

using namespace std;

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  int n;
  cin >> n;
  vector<int> a(n);
  int max2 = 2000;
  for (int& x : a) {
    cin >> x;
    max2 = min(max2, x & -x);
  }
  vector<int> odds;
  int sum = 0;
  for (int i = 0; i < n; ++i) {
    a[i] /= max2;
    if (a[i] % 2) {
      odds.push_back(i);
    }
    sum += a[i];
  }
  vector<int> ans;
  if (odds.size() % 2 == 0) {
    vector<vector<int>> f(n + 1, vector<int>(sum + 1));
    f[0][0] = 1;
    for (int i = 0; i < n; ++i) {
      for (int j = 0; j <= sum; ++j) {
        if (f[i][j]) {
          f[i + 1][j] = 1;
          if (j + a[i] <= sum) {
            f[i + 1][j + a[i]] = 1;
          }
        }
      }
    }
    if (f[n][sum / 2]) {
      ans.push_back(odds.front() + 1);
    }
  }
  cout << ans.size() << '\n';
  for (int x : ans) {
    cout << x << ' ';
  }
  return 0;
}