#include <bits/stdc++.h>
#define ll long long
#define ull unsigned ll
#define f first
#define s second
#define pii pair<int,int>
#define pll pair<ll,ll>
#define pb push_back
#define epb emplace_back
using namespace std;
const int nmax = 500001;
vector <pll> Dijkstra(int s, int n, vector<vector<int>>&g, vector<ll>&a) {
vector <pll> d(n + 1, make_pair(1e18, 1e18));
priority_queue<pll,vector<pll>, greater<pll>>pq;
vector <bool> used(n + 1, false);
d[s] = {0, 0};
pq.push({0, s});
while(!pq.empty()) {
int v = pq.top().s;
pq.pop();
if(used[v]) continue;
used[v] = true;
for(auto to : g[v]) {
ll nl = max(d[v].f + 1, a[to]);
ll nh = max(d[v].s, a[to]);
if(d[to] > make_pair(nl, nh)) {
d[to] = {nl, nh};
pq.push({d[to].f, to});
}
}
}
return d;
}
int main() {
int n; cin >> n;
int m; cin >>m;
vector <ll> a(n + 1);
for(int i = 1; i <= n; i++) cin >> a[i];
vector <vector<int>>g(n + 1);
for(int i = 1; i <= m; i++) {
int u, v; cin >> u >> v;
g[u].pb(v);
g[v].pb(u);
}
vector<pll>d1 = Dijkstra(1, n, g, a);
vector <pll> d2 = Dijkstra(n, n, g, a);
ll ans = 1e18;
for(int i = 1; i <= n; i++) {
ll x = d1[i].f + d2[i].f;
if(d1[i].s == a[i] && d2[i].s == a[i])
ans = min(ans, x);
}
cout << ans << '\n';
return 0;
}
