import sys
from collections import defaultdict

from typing import List, Tuple


def int1(x: str, /): return int(x) - 1


def input(): return sys.stdin.readline().rstrip('\n')


def dbg(*args, **kwargs):
    print(*(repr(arg) for arg in args), *(f'{k}: {repr(v)}' for k, v in kwargs.items()), sep='; ', file=sys.stderr)


def solve(a):
    l, r = 0, len(a) - 1
    ans = 0
    while l < r:
        if a[l] + a[r] < 0:
            l += 1
            r -= 1
            ans += 1
        else:
            r -= 1
    return ans


def solve0(a):
    s = defaultdict(int)
    ans = 0
    for i in a:
        s[i] += 1
    for i in a:
        c = min(s[-i], 1)
        s[-i] -= c
        ans += c
    return ans // 2


def main():
    n = int(input())
    *a, = sorted(map(int, input().split()))
    return solve(a), solve([-x for x in a[::-1]]), solve0(a)


def _start():
    ret = main()

    if ret is not None:
        if isinstance(ret, List) or isinstance(ret, Tuple):
            print(*ret)
        else:
            print(ret)


if __name__ == '__main__':
    _start()