From beginning till end, this message has been waiting to be conveyed. For a given unordered multiset of n lowercase English letters ("multi" means that a letter may appear more than once), we treat all letters as strings of length 1 , and repeat the following operation n - 1 times: Remove any two elements s and t from the set, and add their concatenation s + t to the set. The cost of such operation is defined to be , where f ( s , c ) denotes the number of times character c appears in string s . Given a non-negative integer k , construct any valid non-empty set of no more than 100 000 letters, such that the minimum accumulative cost of the whole process is exactly k . It can be shown that a solution always exists. The first and only line of input contains a non-negative integer k ( 0 ≤ k ≤ 100 000 ) — the required minimum cost. Output a non-empty string of no more than 100 000 lowercase English letters — any multiset satisfying the requirements, concatenated to be a string. Note that the printed string doesn't need to be the final concatenated string. It only needs to represent an unordered multiset of letters. For the multiset { 'a' , 'b' , 'a' , 'b' , 'a' , 'b' , 'a' , 'b' }, one of the ways to complete the process is as follows: { "ab" , "a" , "b" , "a" , "b" , "a" , "b" }, with a cost of 0 ; { "aba" , "b" , "a" , "b" , "a" , "b" }, with a cost of 1 ; { "abab" , "a" , "b" , "a" , "b" }, with a cost of 1 ; { "abab" , "ab" , "a" , "b" }, with a cost of 0 ; { "abab" , "aba" , "b" }, with a cost of 1 ; { "abab" , "abab" }, with a cost of 1 ; { "abababab" }, with a cost of 8 . The total cost is 12 , and it can be proved to be the minimum cost of the process.