function solution($A) {

    $n = count($A);
    $total = 0;
    $actual = 0;

    if(count($A) == 0){
    	return -1;
    }

    for($i=0;$i<count($A);$i++){
      $total = $total + $A[$i];
    }

    for($i=0;$i<count($A);$i++){


      $right = $total - $actual;
      $teste = $total - $actual - $A[$i];

      if($teste == $actual){
        return $i;
      }


      //echo "Indice: " . $i . "||" . $A[$i] . "|| left: " . $actual . "|| right: " . $right . "|| Teste: " . $teste .  "\r\n";

      $actual = $actual + $A[$i];


    }

    return -1;


}