устата

Etymology
Originally the possessive of, which it can still mean. It does not take the dative ending, but functions as a true postposition. This in turn means that the noun it modifies does not need a different case ending.

Postposition

 * 1) during
 * 2) for, throughout
 * 3)  while
 * 1) for, throughout
 * 2)  while
 * 1)  while
 * 1)  while