353A

#include<bits/stdc++.h>
#define lli long long int
#define vi vector<int>
#define vlli vector<lli>
#define pii pair<int,int>
#define vpi vector<pii>
#define mp unordered_map<char,int>
#define rep(i,a,b) for(int i=a;i<b;i++)
#define ff first
#define ss second
#define nline "\n"
 
#define MOD1 1000000007
#define MOD2 1000000009
using namespace std;
int main()
{
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
 
  int n;cin>>n;
  int l=0,r=0;
  bool flag=false;
  //int x,y;
  for(int x,y; cin>>x>>y;){
 
    if(n==1 && x%2+y%2==1){
      cout<<-1<<nline;
      return 0;
    }
    if(x%2+y%2==1){
      flag=true;
    }
    l+=x;r+=y;
  }
  if (l%2==0 && r%2==0) cout<<0<<nline;
  else if (l%2==1 && r%2==1 && flag) cout<<1<<nline;
  else cout<<-1<<nline;
  return 0;
}