import sys

sys.setrecursionlimit(4000)

data = sys.stdin.read().split()

num_v = int(data[0])
num_e = int(data[1])

adj = [[] for _ in range(num_v + 1)]
cursor = 2

for _ in range(num_e):
    src = int(data[cursor])
    dst = int(data[cursor + 1])
    cursor += 2
    adj[src].append(dst)

pairs = [0] * (num_v + 1)

def find_match(node):
    if visited[node]:
        return False
    visited[node] = True
    for nxt in adj[node]:
        if pairs[nxt] == 0 or find_match(pairs[nxt]):
            pairs[nxt] = node
            return True
    return False

total_matches = 0
for start_node in range(1, num_v + 1):
    visited = [False] * (num_v + 1)
    if find_match(start_node):
        total_matches += 1

print(num_v - total_matches)