560 B | 560 chars
import sys
from math import sqrt, pi, sin, factorial
inp = lambda : sys.stdin.readline()[:-1].strip()
mii = lambda x = " " : [*map(int,inp().split(x))]
mfi = lambda x = " " : [*map(float,inp().split(x))]
ii = lambda : int(inp())
fi = lambda : float(inp())
p = print
def solve():
n = ii()
l = mii()
d = {}
ans = 0
for i in l:
if i < 0:
k = d.get(-i, 0)
if k == 0:
ans += 1
d[-i] = 0
else:
d[i] = 1
return ans
if __name__ == "__main__":
tc = 1
for t in range(1, tc+1):
ret = solve()
p(ret)