#include <bits/stdc++.h>
using namespace std;
#define pii pair<int, int>
const int nx = 2e5+5;
const int INF = 1e9;
int n, m, a[nx], res = INF;
vector<int> adj[nx];
priority_queue<pii, vector<pii>, greater<pii>> pq;
vector<int> dist(int n)
{
vector<int> vs(nx, 0), d(nx, INF);
d[n] = 0;
pq.push({0, n});
while(!pq.empty())
{
auto [cw, u] = pq.top();
pq.pop();
if(vs[u]) continue;
vs[u] = 1;
for(auto v : adj[u])
{
if(d[v] > max(cw + 1, a[v]))
{
d[v] = max(cw + 1, a[v]);
pq.push({d[v], v});
}
}
}
return d;
}
int main()
{
cin.tie(NULL)->sync_with_stdio(false);
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);
}
vector<int> mn = dist(1);
vector<int> mnr = dist(n);
for(int i=1;i<=n;i++) res = min(res, 2 * max(mn[i], mnr[i]));
for(int u=1;u<=n;u++)
{
for(auto v : adj[u])
res = min(res, 2 * max(mn[u], mnr[v]) + 1);
}
cout << res ;
return 0;
}
