#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
template<class T> using V = vector<T>;
using VI = V<int>;
using VL = V<ll>;
using VS = V<string>;
template<class T> using PQ = priority_queue<T, V<T>, greater<T>>;
using graph = V<VI>;
template<class T> using w_graph = V<V<pair<int, T>>>;
#define FOR(i,a,n) for(int i=(a);i<(n);++i)
#define eFOR(i,a,n) for(int i=(a);i<=(n);++i)
#define rFOR(i,a,n) for(int i=(n)-1;i>=(a);--i)
#define erFOR(i,a,n) for(int i=(n);i>=(a);--i)
#define all(a) a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
#define out(y,x) ((y)<0||h<=(y)||(x)<0||w<=(x))
#ifdef _DEBUG
#define line cout << "-----------------------------\n"
#define stop system("pause")
#endif
constexpr ll INF = 1000000000;
constexpr ll LLINF = 1LL << 60;
constexpr ll mod = 1000000007;
constexpr ll MOD = 998244353;
constexpr ld eps = 1e-10;
template<class T>inline bool chmax(T& a, const T& b) { if (a < b) { a = b; return true; }return false; }
template<class T>inline bool chmin(T& a, const T& b) { if (a > b) { a = b; return true; }return false; }
inline void init() { cin.tie(nullptr); cout.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(15); }
template<class T>inline istream& operator>>(istream& is, V<T>& v) { for (auto& a : v)is >> a; return is; }
template<class T, class U>inline istream& operator>>(istream& is, pair<T, U>& p) { is >> p.first >> p.second; return is; }
template<class T>inline V<T> vec(size_t a) { return V<T>(a); }
template<class T>inline V<T> defvec(T def, size_t a) { return V<T>(a, def); }
template<class T, class... Ts>inline auto vec(size_t a, Ts... ts) { return V<decltype(vec<T>(ts...))>(a, vec<T>(ts...)); }
template<class T, class... Ts>inline auto defvec(T def, size_t a, Ts... ts) { return V<decltype(defvec<T>(def, ts...))>(a, defvec<T>(def, ts...)); }
template<class T>inline void print(const T& a) { cout << a << "\n"; }
template<class T, class... Ts>inline void print(const T& a, const Ts&... ts) { cout << a << " "; print(ts...); }
template<class T>inline void print(const V<T>& v) { for (int i = 0; i < v.size(); ++i)cout << v[i] << (i == v.size() - 1 ? "\n" : " "); }
template<class T>inline void print(const V<V<T>>& v) { for (auto& a : v)print(a); }
template<class T>inline T sum(const V<T>& a, int l, int r) { return a[r] - (l == 0 ? 0 : a[l - 1]); }
template<class T>inline void END(T s) { print(s); exit(0); }
void END() { exit(0); }

int main() {
    init();

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

    set<int> a, b;
    FOR(i, 0, n) {
        if (s[i] == '0')a.insert(i);
        if (t[i] == '0')b.insert(i);
    }
    if (a.size() != b.size())END(-1);
    int ans = 0;
    for (; !a.empty(); a.erase(a.begin()), b.erase(b.begin())) {
        ans += (*a.begin() != *b.begin());
    }
    print(ans);

    return 0;
}
#include<bits/stdc++.h>
using namespace std;

long long res=0;
int main(){
	long double x,y,r;
	cin>>x>>y>>r;
	long long L=ceil(x-r),R=floor(x+r);
    r+=1e-14;
	for(int i=L;i<=R;i++){
		if(r*r-(1.0*i-x)*(1.0*i-x)>=0){
            long double yy=sqrt(r*r-(1.0*i-x)*(1.0*i-x));
            long long tmp=floor(y+yy)-ceil(y-yy)+1;
            res+=tmp;
		}

	}
	cout<<res;
	return 0;
}
