#!/usr/bin/env python3
from collections import Counter


# Based on AC/mike.py, except that it prints an arbitrary pair if the answer is not "impossible".
def arbitrary_pair():
    counts = Counter([x for s in sets for x in s])
    least_occurring = sorted(list(counts.items()), key=lambda tup: (tup[1], tup[0]))
    for second in range(1, n + 1):
        for first in range(second):
            a = least_occurring[first][0]
            b = least_occurring[second][0]
            i = next(i for i, s in enumerate(sets) if a in s)
            j = next((j for j, s in enumerate(sets) if i != j and b in s), None)
            if j:
                exit(print(a, b, i + 1, j + 1))


BASE = 1000000007
n = int(input())
L = int(n**0.5)
sets = [list(map(int, input().split()))[1:] for _ in range(n)]
pairs = {}
for i in range(n):
    if len(sets[i]) <= L:
        sets[i].sort()
        for j1 in range(len(sets[i])):
            for j2 in range(j1 + 1, len(sets[i])):
                x = sets[i][j1] + BASE * sets[i][j2]
                if x in pairs:
                    arbitrary_pair()
                pairs[x] = i
    else:
        xs = set(sets[i])
        for j in range(n):
            if i != j:
                overlap = [x for x in sets[j] if x in xs]
                if len(overlap) >= 2:
                    arbitrary_pair()
print("impossible")