#include <bits/stdc++.h>

using namespace std;

#define REP(i,n) for(int i=0; i<(int)(n); i++)
#define FOR(i,b,e) for (int i=(int)(b); i<(int)(e); i++)
#define ALL(x) (x).begin(), (x).end()

const double PI = acos(-1);

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);

  int n;
  cin >> n;
  vector<int> b(n+1);
  REP (i, n+1) cin >> b[i];

  int zero = b[0];
  int one = 0, none = 0;
  REP (i, n+1) {
    one += b[i];
    if (i % 2 == 0)
      none += b[i];
    else
      none -= b[i];
  }

  vector<int> ret(3);
  ret[0] = zero;
  ret[1] = (one - none) / 2;
  ret[2] = (one + none - 2 * zero) / 2;

  int d = 2;
  while (d > 0 && !ret[d]) {
    --d;
  }
  cout << d << endl;

  REP (i, d+1)
    cout << ret[i] << " ";
  cout << endl;

  return 0;
}