//#define _GLIBCXX_DEBUG

#include<bits/stdc++.h>
using namespace std;

#define endl '\n'
#define lfs cout<<fixed<<setprecision(10)
#define ALL(a)  (a).begin(),(a).end()
#define ALLR(a)  (a).rbegin(),(a).rend()
#define spa << " " <<
#define fi first
#define se second
#define MP make_pair
#define MT make_tuple
#define PB push_back
#define EB emplace_back
#define rep(i,n,m) for(ll i = (n); i < (ll)(m); i++)
#define rrep(i,n,m) for(ll i = (ll)(m) - 1; i >= (ll)(n); i--)
using ll = long long;
using ld = long double;
const ll MOD1 = 1e9+7;
const ll MOD9 = 998244353;
const ll INF = 1e18;
using P = pair<ll, ll>;
template<typename T1, typename T2>bool chmin(T1 &a,T2 b){if(a>b){a=b;return true;}else return false;}
template<typename T1, typename T2>bool chmax(T1 &a,T2 b){if(a<b){a=b;return true;}else return false;}
ll median(ll a,ll b, ll c){return a+b+c-max({a,b,c})-min({a,b,c});}
void ans1(bool x){if(x) cout<<"Yes"<<endl;else cout<<"No"<<endl;}
void ans2(bool x){if(x) cout<<"YES"<<endl;else cout<<"NO"<<endl;}
void ans3(bool x){if(x) cout<<"Yay!"<<endl;else cout<<":("<<endl;}
template<typename T1,typename T2>void ans(bool x,T1 y,T2 z){if(x)cout<<y<<endl;else cout<<z<<endl;}  
template<typename T>void debug(vector<vector<T>>&v,ll h,ll w){for(ll i=0;i<h;i++){cout<<v[i][0];for(ll j=1;j<w;j++)cout spa v[i][j];cout<<endl;}};
void debug(vector<string>&v,ll h,ll w){for(ll i=0;i<h;i++){for(ll j=0;j<w;j++)cout<<v[i][j];cout<<endl;}};
template<typename T>void debug(vector<T>&v,ll n){if(n!=0)cout<<v[0];for(ll i=1;i<n;i++)cout spa v[i];cout<<endl;};
template<typename T>vector<vector<T>>vec(ll x, ll y, T w){vector<vector<T>>v(x,vector<T>(y,w));return v;}
ll gcd(ll x,ll y){ll r;while(y!=0&&(r=x%y)!=0){x=y;y=r;}return y==0?x:y;}
vector<ll>dx={1,-1,0,0,1,1,-1,-1};vector<ll>dy={0,0,1,-1,1,-1,1,-1};
template<typename T>vector<T> make_v(size_t a,T b){return vector<T>(a,b);}
template<typename... Ts>auto make_v(size_t a,Ts... ts){return vector<decltype(make_v(ts...))>(a,make_v(ts...));}
template<typename T1, typename T2>ostream &operator<<(ostream &os, const pair<T1, T2>&p){return os << p.first << " " << p.second;}
template<typename T>ostream &operator<<(ostream &os, const vector<T> &v){for(auto &z:v)os << z << " ";cout<<"|"; return os;}
template<typename T>void rearrange(vector<ll>&ord, vector<T>&v){
  auto tmp = v;
  for(int i=0;i<tmp.size();i++)v[i] = tmp[ord[i]];
}
template<typename Head, typename... Tail>void rearrange(vector<ll>&ord,Head&& head, Tail&&... tail){
  rearrange(ord, head);
  rearrange(ord, tail...);
}
//mt19937 mt(chrono::steady_clock::now().time_since_epoch().count());
int popcount(ll x){return __builtin_popcountll(x);};
int poplow(ll x){return __builtin_ctzll(x);};
int pophigh(ll x){return 63 - __builtin_clzll(x);};

int main(){
  cin.tie(nullptr);
  ios_base::sync_with_stdio(false);
  ll res=0,buf=0;
  bool judge = true;
  ll n;cin>>n;
  string s,t;cin>>s>>t;
  vector<ll>l,r;
  rep(i,0,n)if(s[i]=='1')l.PB(i);
  rep(i,0,n)if(t[i]=='1')r.PB(i);
  ll idx=0;
  rep(i,0,l.size()){
    if(idx==r.size()||l[i]<r[idx]){
      if(i+2>l.size()){
        judge=false;
        break;
      }
      res+=l[i+1]-l[i];
      i++;
    }
    else{
      res+=l[i]-r[idx];
      idx++;
    }
    //cout<<i spa res<<endl;
  }
  if(idx!=r.size())judge=false;
  ans(judge,res,-1);
  return 0;
}
#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cmath>
#include<cstring>
#include<algorithm>
#include<climits>
#include<utility>
#include<vector>
#include<queue>
#define int long long
using namespace std;
const int MaxN = 500005;
int n, ans;
char s[MaxN], t[MaxN];
queue<int> pos;

inline int Read(){
	int num = 0, op = 1;
	char ch = getchar();
	while(!isdigit(ch)){
		if(ch == '-') op = -1;
		ch = getchar();
	}
	while(isdigit(ch)){
		num = num * 10 + ch - '0';
		ch = getchar();
	}
	return num * op;
}

signed main(){
	n = Read();
	scanf("%s%s", s+1, t+1);
	for(int i=1; i<=n; i++)
		if(s[i] == '1') pos.push(i);
	for(int i=1; i<=n; i++){
		if(s[i] == t[i]){
			if(s[i] == '1') pos.pop();
			continue;
		}
		else if(s[i] == '1' && t[i] == '0'){
			if(pos.empty()){
				printf("-1");
				return 0;
			}
			int p1 = pos.front();
			pos.pop();
			if(pos.empty()){
				printf("-1");
				return 0;
			}
			int p2 = pos.front();
			pos.pop();
			ans += (p2 - p1);
			s[p1] = s[p2] = '0';
		}
		else if(s[i] == '0' && t[i] == '1'){
			if(pos.empty()){
				printf("-1");
				return 0;
			}
			int p = pos.front();
			pos.pop();
			ans += (p - i);
			s[p] = '0', s[i] = '1';
		}
	}
	printf("%lld", ans);
	return 0;
}