Hi everyone i was trying this question from Atcoder — https://atcoder.jp/contests/abc157/tasks/abc157_e But im getting runtime error on my code. My approach is to build a segment tree where each node contains a map of charaters. And while we go up we keep on merging the maps into a single map and the return the size of the map as a answer to the query. Im not getting any WA but RE. Please help. Here is my submission https://atcoder.jp/contests/abc157/submissions/47573702