#include <bits/stdc++.h>
using namespace std;
#define int long long
const int mod = 1e9+7;
struct dsu{
int n;
vector<int> p, s;
vector<set<int>> st;
dsu(int _n, vector<int> g){
n = _n;
p.resize(n);
s.resize(n, 1);
st.resize(n);
iota(p.begin(), p.end(), 0);
}
int find(int x){
if(x==p[x]) return x;
return p[x] = find(p[x]);
}
int op(int x){
int t = find(x);
while(*st[t].begin()<=x&&st[t].size()>1){
st[t].erase(st[t].begin());
}
return *st[t].begin();
}
int merge(int u, int v){
u = find(u);
v = find(v);
if(u==v) return 0;
if(s[u]<s[v]) swap(u, v);
s[u] += s[v];
p[v] = u;
if(st[u].size() < st[v].size()){
swap(st[u], st[v]);
}
for(auto i: st[v]) st[u].insert(i);
return 1;
}
};
struct LCA {
int root, n, cnt;
vector<vector<int>> adj;
vector<array<int, 21>> par;
vector<int> ti, to, d;
LCA(vector<vector<int>> aadj, int r){
adj = aadj; n = adj.size();
par.resize(n);
d.assign(n, 0);
root = r; cnt = 0;
ti.resize(n); to.resize(n);
d[root] = -1;
dfs(root, root);
for (int i = 1; i < 21; i++){
for(int l = 0; l<n; l++){
par[l][i] = par[par[l][i-1]][i-1];
}
}
}
void dfs(int v, int p){
par[v][0] = p;
ti[v] = cnt++;
d[v] = d[p]+1;
for (auto i: adj[v]){
if (i != p) dfs(i, v);
}
to[v] = cnt++;
}
bool ia(int u, int v){
return ti[u] <= ti[v] && to[u] >= to[v];
}
int operator()(int u, int v){
if(ia(u, v)) return u;
if(ia(v, u)) return v;
for(int i = 20; i>=0; i--){
if(!ia(par[u][i], v)) u=par[u][i];
}
return par[u][0];
}
int distance(int u, int v){
return d[u]+d[v]-2*d[(*this)(u, v)];
}
};
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
int n; cin >> n;
vector<int> val(n), id(n);
vector<vector<int>> g(n);
for(auto &i: val) cin >> i, i--;
dsu d(n, val);
iota(id.begin(), id.end(), 0);
sort(id.begin(), id.end(), [&](int x, int y){
return val[x] < val[y];
});
for(int i=0; i<n-1; i++){
int x, y; cin >> x >> y;
x--; y--;
d.st[val[x]].insert(val[y]);
d.st[val[y]].insert(val[x]);
g[x].push_back(y);
g[y].push_back(x);
}
LCA lca(g, 0);
vector<vector<int>> g2(n);
int root = -1;
for(auto i: id){
if(val[i]==n-1){
root = i;
break;
}
int pf = d.op(val[i]);
d.merge(pf, val[i]);
g2[id[pf]].push_back(i);
}
int ans = 0;
auto dfs = [&](int v, int z, auto&& dfs)->void{
ans = max(ans, z);
for(auto i: g2[v]){
dfs(i, z+lca.distance(v, i), dfs);
}
};
dfs(root, 0, dfs);
cout << ans;
}
