#嘘解法（ SCC を行わない）

import sys
input = sys.stdin.readline

N,M = map(int,input().split())

source = [True]*N
sink = [True]*N

for _ in [0]*M:
    a,b = map(int,input().split())
    source[a-1] = sink[b-1] = False

ans = max(sum(source),sum(sink))
print(ans)