#include <bits/stdc++.h>
#define fast cin.tie(0)->sync_with_stdio(0);
#define int long long
#define inf ((int)1e18)
using namespace std;
typedef array<int, 2> info; // min k, min altitude
int32_t main(){
fast
int n, m;
cin >> n >> m;
vector <int> arr(n + 1);
vector <vector<int> > adj(n + 1);
for(int i = 1; i <= n; i++) {
cin >> arr[i];
}
for(int i = 0; i < m; i++) {
int a, b;
cin >> a >> b;
adj[a].push_back(b);
adj[b].push_back(a);
}
vector <info> about(n + 1, {inf, inf}), ans;
priority_queue<pair<info, int> > pq;
pq.push({{0, 0}, 1});
bitset <200005> vis;
while(!pq.empty()) {
int node = pq.top().second;
info values = pq.top().first;
pq.pop();
if(vis[node]) continue;
vis[node] = 1;
int k = -values[0], mn = values[1];
// cout << node << ": " << k << " " << mn << "\n";
k++, mn--;
for(auto to:adj[node]) {
int alt = arr[to];
info infTo = {k + max(0ll, alt - k), max(mn, alt)};
if(infTo[0] < about[to][0]) {
about[to] = infTo;
if(to == n) {
ans.push_back(infTo);
}
infTo[0] *= -1;
pq.push({infTo, to});
}
}
}
int aaa = inf;
for(auto it:ans) {
// cout << it[0] << " " << it[1] << "\n";
aaa = min(aaa, it[0] + max(0ll, it[1]));
}
cout << aaa;
}
