from collections import deque
from collections import defaultdict
import copy

def solve():
	n, m = map(int, input().split())
	node_pair = []
	for _ in range(m):
		a, b = map(int, input().split())
		node_pair.append([a, b])
	node_dict = defaultdict(list)
	for pair in node_pair:
		node_dict[pair[0]].append(pair[1])
		node_dict[pair[1]].append(pair[0])
	
	squares = set()	
	for i in range(n):
		pairs = deque()
		pairs.append([i])
		while len(pairs) > 0:
			pair = pairs.popleft()
			connect_nodes = node_dict[pair[-1]]
			for node in connect_nodes:
				if node not in pair:
					tpair = copy.deepcopy(pair)
					tpair.append(node)
					if len(tpair) == 4:
						if tpair[0] in node_dict[tpair[-1]]:
							tpair.sort()
							squares.add(tuple(tpair))
					else:
						pairs.append(tpair)
	ans = 0
	for square in squares:
		for idx in range(4):
			connection_count = 0
			for node in node_dict[square[idx]]:
				if node in square:
					connection_count += 1
			if connection_count != 2:
				break
		else:
			ans += 1 
	print(ans)


if __name__=="__main__":
    solve()