CF827A String Reconstruction

Ivan had string $ s $ consisting of small English letters. However, his friend Julia decided to make fun of him and hid the string $ s $ . Ivan preferred making a new string to finding the old one. Ivan knows some information about the string $ s $ . Namely, he remembers, that string $ t_{i} $ occurs in string $ s $ at least $ k_{i} $ times or more, he also remembers exactly $ k_{i} $ positions where the string $ t_{i} $ occurs in string $ s $ : these positions are $ x_{i,1},x_{i,2},...,x_{i,ki} $ . He remembers $ n $ such strings $ t_{i} $ . You are to reconstruct lexicographically minimal string $ s $ such that it fits all the information Ivan remembers. Strings $ t_{i} $ and string $ s $ consist of small English letters only.

The first line contains single integer $ n $ ( $ 1

Print lexicographically minimal string that fits all the information Ivan remembers.