#include <iostream>
#include <string>
#include <stdio.h>
#include <stdint.h>
using namespace std;

using uint = unsigned int;
using ll = long long;

#define CIN( LL , A ) LL A; cin >> A 
#define FOR_LL( VAR , INITIAL , FINAL_PLUS_ONE ) for( ll VAR = INITIAL ; VAR < FINAL_PLUS_ONE ; VAR ++ ) 
#define RETURN( ANSWER ) cout << ( ANSWER ) << endl; return 0 

int main()
{
  CIN( ll , N );
  ll A[10001];
  FOR_LL( i , 0 , N ){
    cin >> A[i];
  }
  ll count = 0;
  FOR_LL( i , 0 , N ){
    ll& Ai = A[i];
    FOR_LL( j , i + 1 , N ){
      if( Ai > A[j] ){
	count++;
      }
    }
  }
  RETURN( count % 2 == 0 ? 1 : -1 );
}