#include <bits/stdc++.h>
#define int long long
#define pii pair<int, int>
using namespace std;
const int N = 2e5 + 5, INF = 1e18 + 5;
int n, m, w[N]; pii a[N];
vector<int> adj[N];
vector<int> go(int s){
vector<bool> mark(n + 1, false);
vector<int> d(n + 1, INF);
d[s] = 0;
for(int i = 1; i <= n; i++){
int j = a[i].second;
for(int x : adj[j]){
if(mark[x]) d[j] = min(d[j], d[x] + 1 + max(0LL, w[j] - w[x] - 1));
}
for(int x : adj[j]){
if(mark[x]) d[x] = min(d[x], d[j] + 1);
}
mark[a[i].second] = true;
}
return d;
}
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cin >> n >> m;
for(int i = 1; i <= n; i++){
cin >> a[i].first; a[i].second = i;
w[i] = a[i].first;
}
for(int i = 1; i <= m; i++){
int x, y; cin >> x >> y;
adj[x].push_back(y), adj[y].push_back(x);
}
sort(a + 1, a + n + 1);
vector<int> d1 = go(1);
vector<int> dn = go(n);
int ans = INF;
for(int i = 2; i < n; i++){
ans = min(ans, d1[i] + dn[i]);
}
cout << ans << '\n';
return 0;
}
