#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
#define _GLIBCXX_DEBUG
using namespace std;
using std::cout;
using std::cin;
using std::endl;
using ll=long long;
using ld=long double;
ll ILL=2167167167167167167;
const int INF=2100000000;
const ll mod=998244353;
#define rep(i,a) for (ll i=0;i<a;i++)
#define all(p) p.begin(),p.end()
template<class T> using _pq = priority_queue<T, vector<T>, greater<T>>;
template<class T> ll LB(vector<T> &v,T a){return lower_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> ll UB(vector<T> &v,T a){return upper_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> bool chmin(T &a,const T &b){if(a>b){a=b;return 1;}else return 0;}
template<class T> bool chmax(T &a,const T &b){if(a<b){a=b;return 1;}else return 0;}
template<class T> void So(vector<T> &v) {sort(v.begin(),v.end());}
template<class T> void Sore(vector<T> &v) {sort(v.begin(),v.end(),[](T x,T y){return x>y;});}
void yneos(bool a){if(a) cout<<"Yes\n"; else cout<<"No\n";}
template<class T> void vec_out(vector<T> &p){for(int i=0;i<(int)(p.size());i++){if(i) cout<<" ";cout<<p[i];}cout<<"\n";}


void solve();
// oddloop
int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	
	int t=1;
	//cin>>t;
	rep(i,t) solve();
}

void solve(){
	int N;
	cin>>N;
	string S,T;
	cin>>S>>T;
	auto f=[](char a,char b)->char{
		if(a==b) return '0';
		return '1';
	};
	vector<int> ans;
	rep(i,N){
		if(S[i]==T[i]&&S[i+N]==T[i+N]) continue;
		else if(f(S[i],S[i+1])==T[i]&&T[i+1]==S[i]){
			ans.push_back(i);
			ans.push_back(i+1);
		}else if(S[i+1]==T[i]&&f(S[i],S[i+1])==T[i+N]){
			ans.push_back(i+N);
			ans.push_back((i+N+1)%(2*N));
		}else{
			cout<<"-1\n";
			return ;
		}
	}
	cout<<ans.size()<<"\n";
	for(auto x:ans) cout<<x<<"\n";
}