#!/usr/bin/env python3
n = int(input())
p = sorted(list(tuple(map(int, input().split())) for _ in range(n)))
s = (sum(x[0] for x in p), sum(x[1] for x in p))
if n%2 or s[0]%(n//2) != 0 or s[1]%(n//2) != 0:
    print("impossible")
    exit(0)
s = (s[0]/(n//2), s[1]/(n//2))
for a, b in zip(p, reversed(p)):
    if (a[0]+b[0], a[1]+b[1]) != s:
        print("impossible")
        exit(0)
print('possible')