give stre num represent nonnegative integer num integer k return small possible integer remove k digits num Example 1input num 1432219 k 3output 1219explanation Remove digit 4 3 2 form new number 1219 smallestexample 2input num 10200 k 1output 200Explanation Remove lead 1 number 200 note output contain lead zeroesexample 3input num 10 k 2output 0explanation Remove digit number leave 0 Constraints1 k numlength 105num consist digitsnum lead zero zero