#include <bits/stdc++.h>   using namespace std;   const int N = 5000005;   using ll = long long;   ll f[N], pre[N];   int n, a[N];   vector<int> ans;   void move(int x) {     if (x == n || a[x] == 0 || a[x + 1] == 0) return;     ans.push_back(x);     int t = min(a[x], a[x + 1]);     a[x] -= t;     a[x + 1] -= t;   }   int main() {     ios::sync_with_stdio(false);     cin >> n;     for (int i = 1; i <= n; i++) cin >> a[i];     f[2] = a[1];     for (int i = 3; i <= n + 1; i++)       if (f[i - 3] + max(a[i - 1], a[i - 2]) < f[i - 2] + a[i - 1])         f[i] = f[pre[i] = i - 3] + max(a[i - 1], a[i - 2]);       else         f[i] = f[pre[i] = i - 2] + a[i - 1];     for (int i = f[n] < f[n + 1] ? n : n + 1; i > 1; i = pre[i])       if (pre[i] == i - 3) {         move(i - 2), move(i - 1);         if (i > 3) move(i - 3);       } else {         move(i - 1);         if (i > 2) move(i - 2);       }     cout << ans.size() << endl;     for (auto &i : ans) cout << i << endl;     return 0;   }   