#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
template <typename T>
vector<T>& operator--(vector<T>& v) {
  for (auto& i : v) --i;
  return v;
}
template <typename T>
vector<T>& operator++(vector<T>& v) {
  for (auto& i : v) ++i;
  return v;
}
template <typename T>
istream& operator>>(istream& is, vector<T>& v) {
  for (auto& i : v) is >> i;
  return is;
}
template <typename T>
ostream& operator<<(ostream& os, vector<T> v) {
  for (auto& i : v) os << i << ' ';
  return os;
}
template <typename T, typename U>
pair<T, U>& operator--(pair<T, U>& p) {
  --p.first;
  --p.second;
  return p;
}
template <typename T, typename U>
pair<T, U>& operator++(pair<T, U>& p) {
  ++p.first;
  ++p.second;
  return p;
}
template <typename T, typename U>
istream& operator>>(istream& is, pair<T, U>& p) {
  is >> p.first >> p.second;
  return is;
}
template <typename T, typename U>
ostream& operator<<(ostream& os, pair<T, U> p) {
  os << p.first << ' ' << p.second;
  return os;
}
template <typename T, typename U>
pair<T, U> operator-(pair<T, U> a, pair<T, U> b) {
  return make_pair(a.first - b.first, a.second - b.second);
}
template <typename T, typename U>
pair<T, U> operator+(pair<T, U> a, pair<T, U> b) {
  return make_pair(a.first + b.first, a.second + b.second);
}
template <typename T, typename U>
void umin(T& a, U b) {
  if (a > b) a = b;
}
template <typename T, typename U>
void umax(T& a, U b) {
  if (a < b) a = b;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int n;
  cin >> n;
  if (n == 1) {
    cout << 0 << '\n';
    return 0;
  }
  vector<ll> a(n);
  cin >> a;
  vector<ll> dp(n + 1, 1e18);
  dp[0] = 0;
  dp[1] = a[0];
  for (int i = 2; i <= n; ++i) {
    dp[i] = min(dp[i], dp[i - 2] + a[i - 1]);
    if (i >= 3) dp[i] = min(dp[i], dp[i - 3] + max(a[i - 1], a[i - 2]));
  }
  int x = n;
  if (dp[n - 1] < dp[n]) x = n - 1;
  vector<int> ans;
  while (x > 0) {
    if (x == 1 || dp[x] == dp[x - 2] + a[x - 1]) {
      ans.push_back(x - 1);
      ans.push_back(x - 2);
      x -= 2;
    } else {
      ans.push_back(x - 2);
      ans.push_back(x - 1);
      ans.push_back(x - 3);
      x -= 3;
    }
  }
  ll s = min(dp[n - 1], dp[n]);
  ll tot = 0;
  vector<int> real_ans;
  for (int k : ans) {
    if (k < 0 || k + 1 >= n) continue;
    ll m = min(a[k], a[k + 1]);
    if (m) real_ans.push_back(k);
    tot += m;
    a[k] -= m;
    a[k + 1] -= m;
  }
  assert(s == tot);
  cout << real_ans.size() << '\n';
  for (int k : real_ans) {
    cout << k + 1 << '\n';
  }
  return 0;
}
