#!/usr/bin/env python3
import sys
INF = float("inf")


def solve(N: int, v: "List[int]"):
    v.sort()
    curr = (v[0] + v[1])/2
    for i in range(2, N):
        curr = (curr + v[2])/2
    print(curr)

    return


def main():

    def iterate_tokens():
        for line in sys.stdin:
            for word in line.split():
                yield word
    tokens = iterate_tokens()
    N = int(next(tokens))  # type: int
    v = [int(next(tokens)) for _ in range(N)]  # type: "List[int]"
    solve(N, v)


if __name__ == '__main__':
    main()
