# coding: utf-8
import numpy as np
n=int(input())
a=[i for i in range(n+1)]
for i in range(int(input())):
    tx,ty=map(int,input().split())
    a[tx],a[ty]=a[ty],a[tx]
ar=np.zeros((n,n))
for i in range(n):
    ar[i][a[i+1]-1]=1
I=p=np.identity(n)
for i in range(1,1000000000):
    p=p@ar
    if np.allclose(p,I)==True:
        print(i)
        break;