#!/usr/bin/env python
# -*- coding: utf-8 -*-

from __future__ import (division, absolute_import, print_function,
                        unicode_literals)


def average(array):

    plants = set(array)
    return sum(plants) / len(plants)


if __name__ == '__main__':
    n = int(input())
    arr = list(map(int, input().split()))
    result = average(arr)
    print(result)

#!/usr/bin/env python
# -*- coding: utf-8 -*-

from __future__ import (division, absolute_import, print_function,
                        unicode_literals)


def average(array):

    plants = set(array)
    return sum(plants) / len(plants)


if __name__ == '__main__':
    n = int(input())
    arr = list(map(int, input().split()))
    result = average(arr)
    print(result)

#!/usr/bin/env python # -*- coding: utf-8 -*-