text: cover the base cases
code: if ( arr [ 0 ] == ' I ' ) { v . push_back ( 1 ) ; v . push_back ( 2 ) ; min_avail = 3 ; pos_of_I = 1 ; } else { v . push_back ( 2 ) ; v . push_back ( 1 ) ; min_avail = 3 ; pos_of_I = 0 ; }