#include <iostream>
#include <iomanip>
#include <vector>
#include <cmath>
#include <algorithm>
#include <set>
#include <queue>
#include <map>
#include <unordered_map>
#include <stack>
#include <bit>
#include <bitset>
#include <string>
#include <cstring>
#include <iterator>
#include <random>
#define ll long long
#define ld long double
#define inf (ll)(2*1e18)
#define sort(a) sort(a.begin(), a.end())
#define reverse(a) reverse(a.begin(), a.end())
#define pb push_back
#define endl "\n"
using namespace std;
void Dijkstra(ll start, vector<ll>& a, vector<vector<ll>>& b, vector<ll>& dis){
set<pair<ll, ll>> s;
s.insert({0, start});
dis[start] = 0;
while(!s.empty()){
auto [val, x] = *s.begin();
s.erase(s.begin());
for(auto y: b[x]){
if(dis[y] > max(a[y], val+1)){
s.erase({dis[y], y});
dis[y] = max(a[y], val+1);
s.insert({dis[y], y});
}
}
}
}
void solve(){
ll n, m, i, x, y, res=inf;
cin>>n>>m;
vector<ll> a(n);
vector<vector<ll>> b(n);
vector<ll> dis1(n, inf);
vector<ll> dis2(n, inf);
for(i=0;i<n;++i){
cin>>a[i];
}
for(i=0;i<m;++i){
cin>>x>>y;
--x;
--y;
b[x].pb(y);
b[y].pb(x);
}
Dijkstra(0, a, b, dis1);
Dijkstra(n-1, a, b, dis2);
for(i=0;i<n;++i){
res = min(res, 2*max(dis1[i], dis2[i]));
for(auto el: b[i]){
if(dis1[i] == dis2[el]){
res = min(res, 2*dis1[i] + 1);
}
}
}
cout<<res<<endl;
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
srand(time(nullptr));
ll t=1;
// cin>>t;
for(;t>0;--t){
solve();
}
return 0;
}
