#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ld long double
#define MOD 998244353
const int N = 200005;
ll n, h[N];
vector<int> g[N];
vector<ll> dijkstra(ll src)
{
vector<ll> dist(n + 1, 1e9);
priority_queue<pair<ll, ll>, vector<pair<ll, ll>>, greater<pair<ll, ll>>> pq;
pq.push({0, src});
while (!pq.empty())
{
auto [w, u] = pq.top();
pq.pop();
if (w > dist[u])
{
continue;
}
for (auto i : g[u])
{
if (max(h[i], w + 1) < dist[i])
{
dist[i] = max(h[i], w + 1);
pq.push({dist[i], i});
}
}
}
return dist;
}
void solve()
{
ll m, u, v, ans = 1e9;
cin >> n >> m;
for (int i = 1; i <= n; i++)
{
cin >> h[i];
}
for (int i = 0; i < m; i++)
{
cin >> u >> v;
g[u].push_back(v);
g[v].push_back(u);
}
vector<ll> d1 = dijkstra(1), dn = dijkstra(n);
for (int i = 1; i <= n; i++)
{
ans = min(ans, d1[i] + dn[i]);
}
cout << ans << '\n';
}
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int tests = 1;
// cin >> tests;
for (int i = 1; i <= tests; i++)
{
solve();
}
return 0;
}
