f=lambda:map(int,input().split())
n,m=f()
*h,=f()
G=[[]for _ in[0]*n]
for _ in[0]*m:
 a,b=f();a-=1;b-=1
 if h[a]<h[b]:a,b=b,a
 G[a]+=b,
*r,=range(n)
r.sort(key=lambda i:h[i])
p=[-1e9]*2*n
p[0]=p[2*n-1]=1
k=0
for i in range(2*n):
 j=r[i%n]
 l=i//n*n
 for t in G[j]:p[j+l]=max(p[j+l],p[t+l]+1)
 k=max(k,p[j]+p[j+n])
print(k-1)