f=lambda:map(int,input().split())
n,m=f()
*h,=f()
G=[]
for _ in[0]*m:
 a,b=f();a-=1;b-=1
 if h[a]>h[b]:a,b=b,a
 G+=(h[a],a,b),(h[a],a+n,b+n)
G.sort()
p=[-1e9]*2*n
p[0]=p[2*n-1]=1
k=0
for _,a,b in G:
 p[b]=max(p[b],p[a]+1)
 k=max(k,p[b%n]+p[b%n+n])
print(k-1)