Background

Description

Loop over the given array of strings to build a result string like this: when a string appears the 2nd, 4th, 6th, etc. time in the array, append the string to the result. Return the empty string if no string appears a 2nd time.

Format

Input

Output

Samples

"a" "b" "a"

"a"

"a" "b" "a" "c" "a" "d" "a"

"aa"

"a" "" "a"

"a"

Limitation

1s, 1024KiB for each test case.