#include <bits/stdc++.h>
using namespace std;
#define int long long
#define ll long long
#define rep(i,a,b) for (int i = a; i <= b; i++)
#define per(i,a,b) for (int i = a; i >= b; i--)
#define fi first
#define se second
#define pii pair<int,int>
#define pb push_back
const int MAXN = 2e5+10;
const int INF = 1e18 + 5;
const int MOD = 1e9+7;
vector<int> g[MAXN];
int dist[MAXN][2],a[MAXN],n;
bool mk[MAXN];
void dijkstra(int u, int k) {
rep(i,1,n) mk[i] = 0;
priority_queue<pii,vector<pii>,greater<pii>> pq;
pq.push({0,u});
dist[u][k] = 0;
while(!pq.empty()) {
auto [d,cur] = pq.top();pq.pop();
if (mk[cur]) continue;
mk[cur] = 1;
for (int &v : g[cur]) {
int w = max(1LL, a[v]-d);
if (dist[v][k] <= d + w) continue;
dist[v][k] = d+w;
pq.push({d+w,v});
}
}
}
void solve() {
int m;cin >> n >> m;
rep(i,1,n) cin >> a[i], dist[i][0] = dist[i][1] = INF;
rep(i,1,m) {
int u,v;cin >> u >> v;
g[u].pb(v);
g[v].pb(u);
}
dijkstra(1,0);
dijkstra(n,1);
int ans = INF;
rep(i,1,n) ans = min(ans, dist[i][0] + dist[i][1] + max(0LL,abs(dist[i][0]-dist[i][1])-1));
//rep(i,1,n) cout << i << ' ' << dist[i][0] << ' ' << dist[i][1] << '\n';
cout << ans << '\n';
}
int32_t main() {
ios_base::sync_with_stdio(0); cin.tie(nullptr);
int tt = 1;
//cin >> tt;
while (tt--) solve();
return 0;
}
