#include <bits/stdc++.h>
#define pb push_back
using namespace std;
int main(){
int n, m;
cin >> n >> m;
vector<int> a(n);
for(int i = 0; i < n; i++){
cin >> a[i];
}
vector<vector<int>> G(n);
for(int i = 0; i < m; i++){
int a, b;
cin >> a >> b;
--a, --b;
G[a].pb(b);
G[b].pb(a);
}
// time, minalt, v
priority_queue<array<int, 3>, vector<array<int, 3>>, greater<array<int, 3>>> q;
vector<int> tstart(n), salt(n);
q.push({0, 0, 0});
vector<bool> vis(n);
vis[0] = 1;
int ans = INT_MAX;
while(!q.empty()){
auto [time, minalt, u] = q.top(); q.pop();
tstart[u] = time;
salt[u] = minalt;
for(int v : G[u]){
if(vis[v]) continue;
vis[v] = 1;
if(time < a[v] - 1){
q.push({a[v], a[v], v}); // kesinlikle v icin minimum sure
} else{
q.push({time+1, max(max(minalt-1, a[v]), 0), v});
}
}
}
q.push({0, 0, n-1});
vis.assign(n, 0);
vector<int> tend(n), ealt(n);
function<int(int)> altdif = [&](int u){
int ret = abs(salt[u] - ealt[u]);
return ret;
};
while(!q.empty()){
auto [time, minalt, u] = q.top(); q.pop();
tend[u] = time;
ealt[u] = minalt;
ans = min(ans, tend[u] + tstart[u] + altdif(u));
for(int v : G[u]){
if(vis[v]) continue;
vis[v] = 1;
if(time < a[v] - 1){
q.push({a[v], a[v], v}); // kesinlikle v icin minimum sure
} else{
q.push({time+1, max(max(minalt-1, a[v]), 0), v});
}
}
}
cout << ans << endl;
}
