#include <iostream>
#include <bits/stdc++.h>
using namespace std;
#define endl "\n"
#define i64 long long
const int N=2e5+10;

void solved(){
    int n;
    cin>>n;
    //cout<<n<<endl;
    vector<vector<int>> a(100,vector<int>(n+3));
    vector<int> d(n+1);
    for(int i=1;i<=n;i++){
        i64 x;
        cin>>x;
        d[i]=x;
        for(int j=0;j<=59;j++){
            if((x>>j)&1) a[j+1][i]=1;
        }
    }
    //for(int j=0;j<=59;j++) a[n+1][j]=0;
    
     
            
    auto cluct=[&](int n){
       for(int i=1;i<=n;i++){
         int max=i;
         for(int j=i+1;j<=60;j++){
              if(fabs(a[j][i])>fabs(a[max][i])) max=j;
         }
         for(int j=1;j<=n+1;j++) {
            swap(a[max][j],a[i][j]);
            //swap(d[max],d[i]);
         }
         if(a[i][i]==0){
            vector<int> ans;
            for(int j=i;j>=1;j--){
                if(a[j][i]==1){
                    ans.push_back(j);
                }
            }
            /*
            cout<<";;;"<<endl;
            for(int j=1;j<=n;j++){
                for(int i=1;i<=20;i++) cout<<a[i][j]<<" \n"[i==20];
            }
            */
            ans.push_back(i);
            cout<<ans.size()<<endl;
            for(auto v:ans) cout<<v<<" ";
            //cout<<i<<endl;
            return ;
         }
         for(int j=1;j<=60;j++){
            if(j!=i){
                int temp=a[j][i]/a[i][i];
                for(int k=1;k<=n+1;k++) a[j][k]-=a[i][k]*temp,a[j][k]=(a[j][k]%2+2)%2;
            }
         }
     }
     cout<<"-1"<<endl;
    
   
    
    };
    if(n>=61) cluct(61);
    else cluct(n);
    
}
signed main(){
     //ios::sync_with_stdio(false);
     //cin.tie(0);
     //cout.tie(0);
     int t=1;
     //cin>>t;
     while(t--) solved();
}