CF899F Letters Removing

Petya has a string of length $ n $ consisting of small and large English letters and digits. He performs $ m $ operations. Each operation is described with two integers $ l $ and $ r $ and a character $ c $ : Petya removes from the string all characters $ c $ on positions between $ l $ and $ r $ , inclusive. It's obvious that the length of the string remains the same or decreases after each operation. Find how the string will look like after Petya performs all $ m $ operations.

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In the first example during the first operation both letters 'a' are removed, so the string becomes "bc". During the second operation the letter 'c' (on the second position) is removed, and the string becomes "b". In the second example during the first operation Petya removes '0' from the second position. After that the string becomes "Az". During the second operations the string doesn't change.