#include <iostream>
#include <fstream>
#include <cassert>
#include <cstdlib>
#include <string>
#include <vector>
#include <set>

using namespace std;

int n;
string s, t;
vector<int> vec;
int zeroS[1005], zeroT[1005];

void ope(int x)
{
	vec.push_back(x%(2*n));
	vec.push_back((x+1)%(2*n));
}

int main()
{
	cin >> n >> s >> t;
	assert(n >= 1 && n <= 500);
	assert(s.size() == 2*n && t.size() == 2*n);
	for(int i = 0; i < s.size(); i++) assert(s[i] == '0' || s[i] == '1');
	for(int i = 0; i < t.size(); i++) assert(t[i] == '0' || t[i] == '1');
	
	for(int i = 0; i < n; i++) if(s[i] == '0' && s[i+n] == '0') zeroS[i] = 1;
	for(int i = 0; i < n; i++) if(t[i] == '0' && t[i+n] == '0') zeroT[i] = 1;
	
	for(int i = 0; i < n; i++){
		if(zeroS[i] != zeroT[i]){
			cout << -1 << endl;
			return 0;
		}
	}
	
	for(int i = 0; i < n; i++){
		if(zeroS[i]) continue;
		if(s[i] == '0' && s[i+n] == '1'){
			if(t[i] == '1' && t[i+n] == '1') ope(i+n);
			if(t[i] == '1' && t[i+n] == '0') ope(i);
		}
		else if(s[i] == '1' && s[i+n] == '0'){
			if(t[i] == '1' && t[i+n] == '1') ope(i);
			if(t[i] == '0' && t[i+n] == '1') ope(i+n);
		}
		else if(s[i] == '1' && s[i+n] == '1'){
			if(t[i] == '0' && t[i+n] == '1') ope(i);
			if(t[i] == '1' && t[i+n] == '0') ope(i+n);
		}
	}
	
	cout << vec.size() << endl;
	for(int i = 0; i < vec.size(); i++) cout << vec[i] << endl;
	
	return 0;
}