#import<bits/stdc++.h>
using namespace std;int n,m,i,a,b,x[100000],h[100000];main(){cin>>n>>m;for(i=0;i<n;i++)cin>>h[i];for(i=0;i<n;i++)x[h[i]-1]=i;vector<vector<int>> g(2*n);for(;m--;){cin>>a>>b;a--;b--;if(h[a]>h[b])swap(a,b);g[a].push_back(b);}vector<int> d(2*n,-1e9);for(d[0] = 1,d[2*n-1]=a=0;i=x[++a]&n;)for(int j:g[i]){if(d[j]<d[i]+1)d[j]=d[i]+1;if(d[j+n]<d[i+n]+1)d[j+n]=d[i+n]+1;}for(a=-1,i=n;i--;)if(d[i]+d[i+n]>a)a=d[i]+d[i+n];cout<<a<<"\n";}