#include <cmath>

class ASum
{
  public:
  static long long findNb(long long m)
  {
    long long result = std::sqrt(std::sqrt(4.0 * m) - 1);

    return (4 * m == (std::pow(result, 2) * std::pow(result + 1, 2))) ? result : -1;
  }
};