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))
    if x not in even:
        even[x] = set()
    if y not in odd:
        odd[y] = set()
    for i,j in points:
        if i == x:
            even[i].add(ind+1)
            even[x].add(ind+1)
        if j == y:
            odd[j].add(ind+1)
            odd[y].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 n in graph[nxt]:
        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


try:
    start = 1
    order.append(1)
    seen.add(1)
    dfs(points[0][0], points[0][1])
    print(-1)
except ConnectionError:
    print(len(order))
    print(" ".join(str(i) for i in order))
    exit()