#include <iostream>
#include <iomanip>
#include <algorithm>
#include <assert.h>
#include <complex>
#include <utility>
#include <vector>
#include <string>
#include <stack>
#include <queue>
#include <tuple>
#include <cmath>
#include <bitset>
#include <cctype>
#include <set>
#include <map>
#include <unordered_map>
#include <numeric>
#include <functional>
#include <chrono>
#define _overload3(_1,_2,_3,name,...) name
#define _rep(i,n) repi(i,0,n)
#define repi(i,a,b) for(ll i=a;i<b;++i)
#define rep(...) _overload3(__VA_ARGS__,repi,_rep,)(__VA_ARGS__)
#define _rrep(i,a) rrepi(i,a,0)
#define rrepi(i,a,b) for(ll i=a-1;i>=b;--i)
#define rrep(...) _overload3(__VA_ARGS__,rrepi,_rrep,)(__VA_ARGS__)
#define all(x) (x).begin(),(x).end()
#define PRINT(V) cout << V << "\n"
#define SORT(V) sort((V).begin(),(V).end())
#define RSORT(V) sort((V).rbegin(), (V).rend())
using namespace std;
using ll = long long;
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; }
inline void Yes(bool condition){ if(condition) PRINT("Yes"); else PRINT("No"); }
template<class itr> void cins(itr first,itr last){
    for (auto i = first;i != last;i++){
        cin >> (*i);
    }
}
template<class itr> void array_output(itr start,itr goal){
    string ans = "",k = " ";
    for (auto i = start;i != goal;i++) ans += to_string(*i)+k;
    if (!ans.empty()) ans.pop_back();
    PRINT(ans);
}
ll gcd(ll a, ll b) {
    return a ? gcd(b%a,a) : b;
}

const ll INF = 1e18;
const ll MOD = 1000000007;
const ll MOD2 = 998244353;
const ll MOD3 = 1e6;
const ll EPS = 1e-10;
int sgn(const double a){
    return (a < -EPS ? -1 : (a > EPS ? +1 : 0));
}
typedef pair<int,int> pi;
typedef pair<ll,ll> P;
typedef tuple<ll,ll,ll> tri;
typedef pair<double,double> point;
typedef complex<double> Point;
typedef string::const_iterator State;
const ll MAX = 125000;
constexpr ll nx[4] = {-1,0,1,0};
constexpr ll ny[4] = {0,1,0,-1};

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    ll n;
    cin >> n;
    ll ans = INF;
    rep(i,n){
        ll a,p,x;
        cin >> a >> p >> x;
        if (x-a > 0) chmin(ans,p);
    }
    if (ans == INF) PRINT(-1);
    else PRINT(ans);
}

#include <bits/stdc++.h>
using namespace std;
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) begin(v),end(v)
template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
template<typename A, typename B> inline bool chmin(A &a, B b) { if (a>b) { a=b; return 1; } return 0; }
using ll = long long;
using pii = pair<int, int>;
constexpr ll INF = 1ll<<30;
constexpr ll longINF = 1ll<<60;
constexpr ll MOD = 1000000007;
constexpr bool debug = 0;
//---------------------------------//

int main() {
	int N;
	cin >> N;
	string S, T;
	cin >> S >> T;
	
	vector<int> A(N + 1), B(N + 1);
	REP(i, N) {
		A[i + 1] = A[i] ^ (S[i] == '1');
		B[i + 1] = B[i] ^ (T[i] == '1');
	}
	
	cout << [&]() -> ll {
		ll ans = 0;
		int pos = -1, col = 0;
		REP(i, N + 1) {
			int cur = i < pos ? A[pos] : A[i];
			
			if (cur != B[i]) {
				++pos;
				chmax(pos, i);
				while (pos <= N && A[pos] != B[i]) ++pos;
				if (pos > N) return -1;
				ans += pos - i;
			}
		}
		return ans;
	}() << endl;
	
	return 0;
}