import sys
from sys import stdin
from collections import deque

def main():
    sys.setrecursionlimit(1 << 25)
    N, M = map(int, stdin.readline().split())
    edges = [[] for _ in range(N+1)]  # 1-based
    in_degree = [0] * (N + 1)
    out_degree = [0] * (N + 1)
    for _ in range(M):
        u, v = map(int, stdin.readline().split())
        edges[u].append(v)
        edges[v].append(u)  # for undirected connectivity
        out_degree[u] += 1
        in_degree[v] += 1

    # Compute connected components in the underlying undirected graph
    visited = [False] * (N + 1)
    C = 0
    for i in range(1, N+1):
        if not visited[i]:
            C += 1
            q = deque()
            q.append(i)
            visited[i] = True
            while q:
                u = q.popleft()
                for v in edges[u]:
                    if not visited[v]:
                        visited[v] = True
                        q.append(v)

    # Compute deltas
    S = 0
    for i in range(1, N+1):
        delta = out_degree[i] - in_degree[i]
        if delta > 0:
            S += delta

    if S == 0:
        # Check if already connected
        if C == 1:
            print(0)
        else:
            print(C - 1)
    else:
        K_circuit = max(S, C - 1)
        K_trail = max(S - 1, C - 1)
        print(min(K_circuit, K_trail))

if __name__ == "__main__":
    main()