the idea is when i find 4 I increase the number of taxis by one, and then i combine every 1's and 3's in one taxi, and i combine 2's with each other , and the remaining 2's and 1's i combine them and divide them by 4 and adds the result to number of taxis , if there is any remaining groups i increase the number of taxis by one . I get wrong answer at test case 64 and i don't know why so please any help . here is my submission code.............< 21109241 thanks in advance :D