A boy goes to 20 of his friend’s houses with ‘n’ number of newly purchased marbles in his hands. At every house he visits , he gives away half of marbles he have and take one of his friend’s marble’s and adds it with the one’s he is left with , he never had a problem of dividing an odd number of marbles left and finally after leaving the his 20th friends house, he is left with 2 marbles, can you guess the ‘n’ value?