#include <bits/stdc++.h>
using namespace std;
#define pii pair<int, int>
const int maxN = 2e5 + 5, inf = 1e9;
int n, m, a[maxN]; pii dis[3][maxN];
vector<int> adj[maxN];
void dijkstra(int type, int st) {
priority_queue<pair<pii, int>, vector<pair<pii, int>>, greater<pair<pii, int>>> pq;
dis[type][st] = {0, 0};
pq.push({dis[type][st], st});
while (pq.size() > 0) {
int len = pq.top().first.first, height = pq.top().first.second, u = pq.top().second; pq.pop();
if (dis[type][u].first != len || dis[type][u].second != height) continue;
for (auto v: adj[u]) {
pair<int, int> nw = {len + max(1, a[v] - len), max(height, a[v])};
if (dis[type][v] > nw) {
dis[type][v] = nw;
pq.push({nw, v});
}
}
}
}
int main() {
ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
cin >> n >> m;
for (int i = 1; i <= n; i++) {
cin >> a[i];
dis[1][i] = dis[2][i] = {inf, 0};
}
for (int i = 1; i <= m; i++) {
int u, v;
cin >> u >> v;
adj[u].push_back(v);
adj[v].push_back(u);
}
dijkstra(1, 1);
dijkstra(2, n);
int ans = inf;
for (int i = 1; i <= n; i++)
if (dis[1][i].second == a[i] && dis[2][i].second == a[i])
ans = min(ans, dis[1][i].first + dis[2][i].first);
cout << ans;
return 0;
}
