from sys import stdin, setrecursionlimit
setrecursionlimit(10**6)

input = stdin.readline
H,W,N = [int(i) for i in input().split()]
odd = {}
even = {}
points = []
for ind in range(N):
    x,y = [int(i) for i in input().split()]
    points.append((x,y))
    even.setdefault(x, {})
    odd.setdefault(y, {})
    for i,j in points:
        if i == x:
            even[i].setdefault(x, set())
            even[x].setdefault(i, set())
            even[i][x].add(ind+1)
            even[x][i].add(ind+1)
        if j == y:
            odd[j].setdefault(y, set())
            odd[y].setdefault(j, set())
            odd[j][y].add(ind+1)
            odd[y][j].add(ind+1)
#
# print(odd)
# print(even)

order = []
seen = set()
start = 0
def dfs(x,y):
    global order, seen
    rodd = len(order)&1
    graph = odd if rodd else even
    nxt = y if rodd else x
    # print(x,y,rodd,order,seen)
    for lst in graph[nxt]:
        gnl = graph[nxt][lst]
        for n in gnl:
            if n not in seen:
                seen.add(n)
                order.append(n)
                i,j = points[n-1]
                dfs(i,j)
                order.pop()
                seen.remove(n)
            else:
                if n == start and len(order) >= 4:
                    # print(order)
                    raise ConnectionError


for ind,(i,j) in enumerate(points):
    # print()
    order.clear()
    seen.clear()
    try:
        start = ind+1
        order.append(ind+1)
        seen.add(ind+1)
        dfs(i,j)
    except ConnectionError:
        print(len(order))
        print(" ".join(str(i) for i in order))
        exit()
print(-1)