#include <bits/stdc++.h>
#pragma GCC optimize("O3")
using namespace std;
using ll = long long;
#define int ll
const int INF = (ll)4e18;
int n;
vector<vector<int>> adj;
vector<int> a;
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
int m; cin >> n >> m;
adj = vector<vector<int>>(n);
a = vector<int>(n); for(int& i : a) cin >> i;
for(int i = 0; i < m; i++) {
int a,b; cin >> a >> b; a--; b--;
adj[a].push_back(b);
adj[b].push_back(a);
}
vector<int> dist(n,INF);
vector<int> minA(n);
priority_queue<array<int,3>, vector<array<int,3>>, greater<array<int,3>>> pq;
pq.push({0,0});
while(!pq.empty()) {
auto [d,mn,curr] = pq.top(); pq.pop();
if(d>dist[curr]) continue;
dist[curr] = max(a[curr],d);
minA[curr] = max(a[curr],mn);
for(int nxt : adj[curr]) {
pq.push({dist[curr]+1,minA[curr]-1,nxt});
}
}
cout << dist[n-1]+minA[n-1];
return 0;
}
