class solution(object): def function(self, a:int, s: list): x, y = s[:r], s[r+a:][::-1] for i in range(r): res.extend([x[i], y[i]]) if a: res.append(s[r]) return res
if __name__ == "__main__" : s = input().split(",") t = len(s) r = t // 2 res = [] q = solution() if t%2==1: q.function(1, s) else: q.function(0, s) print(",".join(res))