#include <bits/stdc++.h>
using namespace std;
template <class T>
inline T BM(T p, T e, T M) {
  long long int ret = 1;
  for (; e > 0; e >>= 1) {
    if (e & 1) ret = (ret * p) % M;
    p = (p * p) % M;
  }
  return (T)ret;
}
template <class T>
inline T gcd(T a, T b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
template <class T>
inline T MDINV(T a, T M) {
  return BM(a, M - 2, M);
}
template <class T>
inline T PW(T p, T e) {
  long long int ret = 1;
  for (; e > 0; e >>= 1) {
    if (e & 1) ret = (ret * p);
    p = (p * p);
  }
  return (T)ret;
}
template <class T>
string NTS(T Number) {
  stringstream ss;
  ss << Number;
  return ss.str();
}
template <class T>
T stringtonumber(const string &Text) {
  istringstream ss(Text);
  T result;
  return ss >> result ? result : 0;
}
template <class T>
bool ISLEFT(T a, T b, T c) {
  if (((a.first - b.first) * (b.second - c.second) -
       (b.first - c.first) * (a.second - b.second)) < 0.0)
    return 1;
  else
    return 0;
}
int main() {
  int n;
  scanf("%d", &n);
  pair<int, int> a[n + 2];
  int res = 0, sum = 0;
  for (int i = 1; i <= n; i++) {
    scanf("%d%d", &a[i].first, &a[i].second);
    a[i].first %= 2;
    a[i].second %= 2;
    res += a[i].first;
    sum += a[i].second;
  }
  if (res % 2 == 0 && sum % 2 == 0) {
    printf("%d\n", 0);
    return 0;
  }
  for (int i = 1; i <= n; i++) {
    if ((res - a[i].first + a[i].second) % 2 == 0 &&
        (sum - a[i].second + a[i].first) % 2 == 0) {
      printf("1");
      return 0;
    }
  }
  printf("-1");
  return 0;
}
