1. An information processor comprising one or more processors configured to at least: acquire a first point of a first part of an object and a second point of a second part of the object measured by a distance sensor, the distance sensor being apart from a reference surface and the object, the first part of the object existing in a first detection range, the second part of the object existing in a second detection range, the first detection range being defined by first and second planes having respective pre-defined first and second distances from the reference surface, the second detection range being different than the first detection range and being defined by third and fourth planes having respective pre-defined third and fourth distances from the reference surface, and an image being displayed on the reference surface; calculate a three-dimensional vector based on the first and the second points; calculate input coordinates of the object based on the three-dimensional vector and at least one of the first detection range and the second detection range, wherein the object is determined to contact the reference surface at a position corresponding to the input coordinates; and determine an input operation by the object based on the three-dimensional vector, the calculated input coordinates, and a position in the image corresponding to the input coordinates.