n,m=map(int,input().split())
assert 2<=n<=1000
assert 1<=m<=2000
edge=[[0]*n for _ in range(n)]
for _ in range(m):
    a,b=map(int,input().split())
    assert 1<=a<=n
    assert 1<=b<=n
    assert a!=b
    a-=1
    b-=1
    assert edge[a][b]==0
    edge[a][b]=1