#include <cstdio>
#include <cstdlib>
#include <iostream>
#include <algorithm>
#include <cstring>
#include <string>
#include <cmath>
using namespace std;
#define MAXN (1005)
long long a[MAXN];
long long ans[MAXN];

int main()
{
	freopen("asm_contribute.in", "r", stdin);
	freopen("asm_contribute.out", "w", stdout);
	int n,i,j;
	int len;
	cin >> n;
	for(i = 1; i <= n; i++)
		cin >> a[i];
	
	for(len = 1; len <= n; len++)
	{
		ans[len] = ans[len-1]^a[len];
		for(i = len+1; i <= n; i++)
		{
			if((a[i]^ans[len]) == 0)
			{
				cout << len+1 << endl;
				for(j = 1; j <= len; j++)
					cout << j << ' ';
				cout << i << endl;
				return 0;
			}
		}
	}
	return 0;
}