#line 1 "main_b.cpp"
#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <cctype>
#include <chrono>
#include <cmath>
#include <complex>
#include <cstdint>
#include <cstdlib>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <limits>
#include <list>
#include <map>
#include <memory>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <type_traits>
#include <unordered_map>
#include <utility>
#include <vector>

/* template start */

using i64 = std::int_fast64_t;
using u64 = std::uint_fast64_t;

#define rep(i, a, b) for (i64 i = (a); (i) < (b); (i)++)
#define all(i) i.begin(), i.end()

#ifdef LOCAL
#define debug(...)                                                    \
  std::cerr << "LINE: " << __LINE__ << "  [" << #__VA_ARGS__ << "]:", \
      debug_out(__VA_ARGS__)
#else
#define debug(...)
#endif

void debug_out() { std::cerr << std::endl; }

template <typename Head, typename... Tail>
void debug_out(Head h, Tail... t) {
  std::cerr << " " << h;
  if (sizeof...(t) > 0) std::cout << " :";
  debug_out(t...);
}

template <typename T1, typename T2>
std::ostream& operator<<(std::ostream& os, std::pair<T1, T2> pa) {
  return os << pa.first << " " << pa.second;
}

template <typename T>
std::ostream& operator<<(std::ostream& os, std::vector<T> vec) {
  for (std::size_t i = 0; i < vec.size(); i++)
    os << vec[i] << (i + 1 == vec.size() ? "" : " ");
  return os;
}

template <typename T1, typename T2>
inline bool chmax(T1& a, T2 b) {
  return a < b && (a = b, true);
}

template <typename T1, typename T2>
inline bool chmin(T1& a, T2 b) {
  return a > b && (a = b, true);
}

template <typename Num>
constexpr Num mypow(Num a, u64 b, Num id = 1) {
  if (b == 0) return id;
  Num x = id;
  while (b > 0) {
    if (b & 1) x *= a;
    a *= a;
    b >>= 1;
  }
  return x;
}

template <typename T>
std::vector<std::pair<std::size_t, T>> enumerate(const std::vector<T>& data) {
  std::vector<std::pair<std::size_t, T>> ret;
  for (std::size_t index = 0; index < data.size(); index++)
    ret.emplace_back(index, data[index]);
  return ret;
}

/* template end */

int main() {
  std::cin.tie(nullptr);
  std::ios::sync_with_stdio(false);

  i64 n;
  std::cin >> n;

  std::string s, t;
  std::cin >> s >> t;

  if (s == t) {
    std::cout << 0 << "\n";
    return 0;
  }

  std::vector<i64> sbit, tbit;

  rep(i, 0, n) {
    if (s[i] == '1') sbit.emplace_back(i);
    if (t[i] == '1') tbit.emplace_back(i);
  }

  i64 snum = sbit.size();
  i64 tnum = tbit.size();

  if (snum < tnum) {
    std::cout << -1 << "\n";
    return 0;
  }

  if ((snum - tnum) % 2 != 0) {
    std::cout << -1 << "\n";
    return 0;
  }

  i64 offset = snum - tnum;

  rep(i, 0, tnum) {
    if (tbit[i] > sbit[i + offset]) {
      std::cout << -1 << "\n";
      return 0;
    }
  }

  i64 ans = 0;
  i64 now = 0;

  rep(i, 0, tnum) {
    while (sbit[now] < tbit[i]) {
      ans += sbit[now + 1] - sbit[now];
      now += 2;
    }
    ans += sbit[now] - tbit[i];
    now++;
  }

  while (now < snum) {
    ans += sbit[now + 1] - sbit[now];
    now += 2;
  }

  std::cout<<ans<<"\n";

  return 0;
}

#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rrep(i, n) for (int i = (int)(n - 1); i >= 0; i--)
#define all(x) (x).begin(), (x).end()
#define sz(x) int(x.size())
using namespace std;
using ll = long long;
const int INF = 1e9;
const ll LINF = 1e18;
template <class T>
void get_unique(vector<T>& x) {
    x.erase(unique(x.begin(), x.end()), x.end());
}
template <class T>
bool chmax(T& a, const T& b) {
    if (a < b) {
        a = b;
        return 1;
    }
    return 0;
}
template <class T>
bool chmin(T& a, const T& b) {
    if (b < a) {
        a = b;
        return 1;
    }
    return 0;
}
template <class T>
vector<T> make_vec(size_t a) {
    return vector<T>(a);
}
template <class T, class... Ts>
auto make_vec(size_t a, Ts... ts) {
    return vector<decltype(make_vec<T>(ts...))>(a, make_vec<T>(ts...));
}
template <typename T>
istream& operator>>(istream& is, vector<T>& v) {
    for (int i = 0; i < int(v.size()); i++) {
        is >> v[i];
    }
    return is;
}
template <typename T>
ostream& operator<<(ostream& os, const vector<T>& v) {
    for (int i = 0; i < int(v.size()); i++) {
        os << v[i];
        if (i < sz(v) - 1) os << ' ';
    }
    return os;
}
int main() {
    int n;
    cin >> n;
    queue<int> s, t;
    rep(i, n) {
        char c;
        cin >> c;
        if (c == '1') s.push(i);
    }
    rep(i, n) {
        char c;
        cin >> c;
        if (c == '1') t.push(i);
    }

    ll ans = 0;
    while (sz(s)) {
        if (!sz(t)) {
            if (sz(s) & 1) {
                ans = -1;
            } else {
                while (sz(s)) {
                    int x = s.front();
                    s.pop();
                    int y = s.front();
                    s.pop();
                    ans += ll(y - x);
                }
            }
            break;
        }

        if (s.front() == t.front()) {
            s.pop();
            t.pop();
        } else if (s.front() < t.front()) {
            if (sz(s) < 2) {
                ans = -1;
                break;
            }
            int x = s.front();
            s.pop();
            int y = s.front();
            s.pop();
            ans += ll(y - x);
        } else {
            int x = s.front();
            s.pop();
            int y = t.front();
            t.pop();
            ans += ll(x - y);
        }
    }
    if (sz(t)) ans = -1;
    cout << ans << '\n';
}