N, M = map(int, input().split())
deg = [0 for _ in range(N)]
indeg = [0 for _ in range(N)]
for _ in range(M):
    u, v = map(int, input().split())
    u-=1
    v-=1
    deg[u] += 1
    indeg[v] += 1
sa = [0 for _ in range(N)]
plus = 0
minus = 0
for i in range(N):
    sa[i] = indeg[i]-deg[i]
    if sa[i]>0:
        plus += sa[i]
    elif sa[i]<0:
        minus += -sa[i]

if plus==0:
    print(0)
else:
    print(plus-1)