// KZ's
#include <fstream>
using namespace std;
ifstream fin ("asm_contribute.in");
ofstream fout ("asm_contribute.out");
///////
int n,s;
unsigned long long ls[1004]={0};
bool vv[1004]={0};
///////
void rin() {
	fin>>n;
	for (int i=1;i<=n;i++)
		fin>>ls[i];
}
void getan() {
	if (s) {
		fout<<s<<endl;
		for (int i=1;i<=n;i++)
			if (vv[i])
				fout<<i<<' ';
		exit(0);
	}
}
void dfs(int i) {
	if (i>n) {
		s=0;
		unsigned long long u=0;
		for (int i=1;i<=n;i++)
			if (vv[i]) {
				s++;
				u^=ls[i];
			}
		if (!u)
			getan();
		return;
	}
	vv[i]=0;
	dfs(i+1);
	vv[i]=1;
	dfs(i+1);
}
/////////
int main() {
	rin();
	dfs(1);
	return 0;
}
// UBWH