#include <iostream>
#include <cstdio>
#include <algorithm>
using namespace std;
#define endl '\n'
#define ll long long
#define pi pair<int, int>
#define f first
#define s second

const int mxn = 500000;
int n;
int a[mxn], b[mxn];

int main(){
	ios::sync_with_stdio(0);
	cin.tie(0);
	
	cin >> n;
	
	for(int i = 0; i < n; i++){
		char c;
		cin >> c;
		a[i] = c & 1;
	} 
	for(int i = 0; i < n; i++){
		char c;
		cin >> c;
		b[i] = c & 1;
	}
	
	ll ret = 0;
	for(int i = 0, j = 0; i < n; i++) if(a[i] != b[i]){
		j = max(j, i + 1);
		while(j < n && !a[j]) j++;
		if(j == n){
			ret = -1;
			break;
		}
		a[j] = 0, ret += j - i;
	}
	
	cout << ret << endl;
	
	return 0;
}
/*
    author:  Maksim1744
    created: 14.11.2020 15:10:32
*/

#include <bits/stdc++.h>

using namespace std;

#define ll   long long
#define ld   long double

#define mp   make_pair
#define pb   push_back
#define eb   emplace_back

#define sum(a)     ( accumulate ((a).begin(), (a).end(), 0ll))
#define mine(a)    (*min_element((a).begin(), (a).end()))
#define maxe(a)    (*max_element((a).begin(), (a).end()))
#define mini(a)    ( min_element((a).begin(), (a).end()) - (a).begin())
#define maxi(a)    ( max_element((a).begin(), (a).end()) - (a).begin())
#define lowb(a, x) ( lower_bound((a).begin(), (a).end(), (x)) - (a).begin())
#define uppb(a, x) ( upper_bound((a).begin(), (a).end(), (x)) - (a).begin())

template<typename T>             vector<T>& operator--            (vector<T>& v){for (auto& i : v) --i;            return  v;}
template<typename T>             vector<T>& operator++            (vector<T>& v){for (auto& i : v) ++i;            return  v;}
template<typename T>             istream& operator>>(istream& is,  vector<T>& v){for (auto& i : v) is >> i;        return is;}
template<typename T>             ostream& operator<<(ostream& os,  vector<T>& v){for (auto& i : v) os << i << ' '; return os;}
template<typename T, typename U> istream& operator>>(istream& is, pair<T, U>& p){is >> p.first >> p.second;        return is;}
template<typename T, typename U> ostream& operator<<(ostream& os, pair<T, U>& p){os << p.first << ' ' << p.second; return os;}
template<typename T, typename U> pair<T,U> operator-(pair<T,U> a, pair<T,U> b){return mp(a.first-b.first, a.second-b.second);}
template<typename T, typename U> pair<T,U> operator+(pair<T,U> a, pair<T,U> b){return mp(a.first+b.first, a.second+b.second);}
template<typename T, typename U> void umin(T& a, U b){if (a > b) a = b;}
template<typename T, typename U> void umax(T& a, U b){if (a < b) a = b;}

#ifdef HOME
#define TAG_LENGTH       25
#define LR_LEFT          left
#define LR_RIGHT         right
#define LR_VALUE         value
#define LR_SECOND_VALUE  mn
#include "C:/C++ libs/print.cpp"
#else
#define showl            42;
#define shows            42;
#define show(...)        42;
#define showm(...)       42;
#define showt(...)       42;
#define printTree(...)   42;
#define printGraph(...)  42;
#define printLRTree(...) 42;
#define printMatrix(...) 42;
#define printWGraph(...) 42;
#define debug     if (false)
#endif

const int inf = 1e9;

int main() {
    ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);

    int n;
    cin >> n;
    string s, t;
    cin >> s >> t;

    vector<int> s1, t1;
    for (int i = 0; i < n; ++i) {
        if (s[i] == '1') {
            s1.pb(i);
        }
        if (t[i] == '1') {
            t1.pb(i);
        }
    }

    if (s1.size() % 2 != t1.size() % 2 || s1.size() < t1.size()) {
        cout << -1 << '\n';
        return 0;
    }

    vector<int> with(t1.size());
    int ind = 0;
    int last = -1;
    vector<bool> u(s1.size(), false);
    for (int i = 0; i < t1.size(); ++i) {
        while (ind < s1.size() && (s1[ind] < t1[i] || (ind - last) % 2 != 1))
            ++ind;
        if (ind == s1.size()) {
            cout << -1 << '\n';
            return 0;
        }
        with[i] = ind;
        u[ind] = true;
        last = ind;
    }

    ll ans = 0;
    last = -1;
    for (int i = 0; i < t1.size(); ++i) {
        ans += s1[with[i]] - t1[i];
    }

    for (int i = 0; i < s1.size(); ++i) {
        if (u[i]) continue;
        if (last == -1) {
            last = s1[i];
        } else {
            ans += s1[i] - last;
            last = -1;
        }
    }
    cout << ans << '\n';

    return 0;
}
