f=lambda:map(int,input().split())
n,m,*G=f()
h=0,*f()
for _ in[k:=0]*m:
 a,b=f()
 if h[a]>h[b]:a,b=b,a
 G+=(h[a],a,b),(h[a],a+n,b+n)
p=[-4*n]*4*n
p[1]=p[2*n]=1
for _,a,b in sorted(G):p[b]=max(p[b],p[a]+1);k=max(k,p[b]+p[b-n])
print(k-1)