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



int main(){
	int n;  cin >> n;
	int ans = 0;
	
	for(int i=1 ; i <= n ; i++){
		int a;  cin >> a;
		
		if(a % 2 != 0) ans++;
	}
	
	if(ans == 0) cout << "-1";
	else
	cout << ans;
	return 0;
}