There are a couple of ducks in a room, they make “quack” sound. Given a string that contains multiple quack words, write a program that returns unique no of ducks in the room. If the string contains incomplete quack word return -1;

//examples
Input: “quackquack” return 2 //two quacks in the string
Input: “qquackuackquack” return 3 // three quacks in the string
Input: “quacqkuack” return 2 //two quacks in the string
Input: “quackqua” return -1 //incomplete quack word in the string
Input: “quackuack” return -1 //incomplete quack word in the string
Input: “qquackuak” return -1 //incomplete quack word in the string