/* Author: Nguyen Chi Thanh - High School for the Gifted - VNU.HCM (i2528) */ #include <bits/stdc++.h> using namespace std; #define int long long #define ull unsigned long long #define ld long double #define pii pair<int, int> #define fi first #define se second #define __builtin_popcount __builtin_popcountll #define all(x) (x).begin(), (x).end() #define BIT(x, i) (((x) >> (i)) & 1) #define MASK(x) ((1ll << (x))) #define debug(a, l, r) for (int _i = (l); _i <= (r); ++_i) cout << (a)[_i] << ' '; cout << '\n'; const int MAXN = 2e5 + 5; const int INF = 1e18 + 5; int n, m, a[MAXN]; int dist1[MAXN], distn[MAXN]; vector<int> adj[MAXN]; void init() { cin >> n >> m; for (int i = 1; i <= n; ++i) cin >> a[i]; for (int i = 1; i <= m; ++i) { int u, v; cin >> u >> v; adj[u].push_back(v); adj[v].push_back(u); } } void dijkstra(int source, int dist[]) { for (int i = 1; i <= n; ++i) dist[i] = INF; dist[source] = 0; priority_queue<pii, vector<pii>, greater<pii>> pq; pq.push({dist[source], source}); while (!pq.empty()) { int cost = pq.top().fi, u = pq.top().se; pq.pop(); if (dist[u] > cost) continue; for (int v : adj[u]) { int cost = max(dist[u] + 1, a[v]); if (dist[v] > cost) { dist[v] = cost; pq.push({dist[v], v}); } } } } void solve() { dijkstra(1, dist1); dijkstra(n, distn); int res = INF; // Relax from all nodes for (int i = 1; i <= n; ++i) { int cost = max(dist1[i], distn[i]); res = min(res, cost * 2); } // Relax from all edges for (int u = 1; u <= n; ++u) { for (int v : adj[u]) { // if (a[u] < a[v]) continue; // cout << u << ' ' << v << '\n'; int cost = 2 * max(dist1[u], distn[v]) + 1; // cout << "Cost: " << cost << '\n'; res = min(res, cost); } } // debug(dist1, 1, n); // debug(distn, 1, n); cout << res; } signed main() { #ifdef NCTHANH freopen("input.txt", "r", stdin); freopen("output.txt", "w", stdout); #endif ios_base::sync_with_stdio(0); cin.tie(nullptr); cout.tie(nullptr); init(); solve(); return 0; }