ll@n;
if(n>61)n=61;
ll@a[n],b[];
rep(k,n)b[k]=1ll<<k;
ll i=n-1;
ll j=59;
while(1){
	rep(k,i+1){
		if(a[k]&1ll<<j){
			swap(a[i],a[k]);
			swap(b[i],b[k]);
			rep(l,k,i){
				if(a[l]&1ll<<j){
					a[l]^=a[i];
					b[l]^=b[i];
				}
			}
			if(--i<0){
				wt(-1);
				exit(0);
			}
			break;
		}
	}
	if(--j<0){
		wt(BIT_popcount(b[i]));
		rep(k,n)if(b[i]&1ll<<k)wtSp(k+1);
		exit(0);
	}
}