// #include <bits/allocator.h> // Temp fix for gcc13 global pragma
// #pragma GCC target("avx2,bmi2,popcnt,lzcnt")
// #pragma GCC optimize("O3,unroll-loops")
#include <bits/stdc++.h>
// #include <x86intrin.h>
using namespace std;
#if __cplusplus >= 202002L
using namespace numbers;
#endif
#ifdef LOCAL
	#include "Debug.h"
#else
	#define debug_endl() 42
	#define debug(...) 42
	#define debug2(...) 42
	#define debugbin(...) 42
#endif



int main(){
	cin.tie(0)->sync_with_stdio(0);
	cin.exceptions(ios::badbit | ios::failbit);
	int n;
	cin >> n;
	vector<long long> a(n);
	copy_n(istream_iterator<long long>(cin), n, a.begin());
	n = min(n, 61);
	vector<long long> basis;
	for(auto bit = 0; bit < 60; ++ bit){
		long long x = 0;
		for(auto i = 0; i < n; ++ i){
			x |= (a[i] >> bit & 1) << i;
		}
		for(auto &b: basis){
			x = min(x, b ^ x);
		}
		if(x == 0){
			continue;
		}
		for(auto &b: basis){
			b = min(b, b ^ x);
		}
		basis.push_back(x);
	}
	if((int)basis.size() == n){
		cout << "-1\n";
		return 0;
	}
	long long pivot = 0;
	for(auto &b: basis){
		pivot |= 1LL << __lg(b);
	}
	for(auto i = 0; i < n; ++ i){
		if(pivot >> i & 1){
			continue;
		}
		vector<int> res{i};
		for(auto &b: basis){
			if(b >> i & 1){
				res.push_back(__lg(b));
			}
		}
		ranges::sort(res);
		cout << (int)res.size() << "\n";
		for(auto i: res){
			cout << i + 1 << " ";
		}
		cout << "\n";
		return 0;
	}
	assert(false);
	return 0;
}

/*

*/