#include <stdio.h>
#include <atcoder/all>
#include <bits/stdc++.h>
using namespace std;
using namespace atcoder;
using mint = modint998244353;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000001
#define Inf64 4000000000000000001LL
void Gauss(vector<bitset<300>> &B){
	int now = 0;
	rep(i,300){
		int temp = -1;
		for(int j=now;j<B.size();j++){
			if(B[j][i]){
				temp = j;
				break;
			}
		}
		if(temp==-1)continue;
		
		rep(j,B.size()){
			if(temp==j)continue;
			if(B[j][i])B[j] ^= B[temp];
		}
		
		swap(B[now],B[temp]);
		now++;
	}
}
int main(){
	
	int n;
	cin>>n;
	vector<long long> a(n);
	rep(i,n)cin>>a[i];
	if(n>70)a.resize(70);
	vector<bitset<300>> cur;
	rep(i,a.size()){
		bitset<300> t;
		rep(j,60){
			if(a[i]>>j&1)t[j] = 1;
		}
		t[60+i] = 1;
		
		cur.push_back(t);
		Gauss(cur);
		bool f = true;
		rep(j,60){
			if(cur.back()[j]){
				f = false;
				break;
			}
		}
		if(f){
			vector<int> ans;
			rep(j,100){
				if(cur.back()[j+60])ans.push_back(j);
			}
			cout<<ans.size()<<endl;
			rep(j,ans.size()){
				if(j!=0)cout<<' ';
				cout<<ans[j]+1;
			}
			cout<<endl;
			return 0;
			
		}
		
	}
	cout<<-1<<endl;
	return 0;
}