#include <bits/stdc++.h>
using namespace std;

const int N = 2e5 + 10;

using pii = pair<int, int>;
vector<int> g[N];

int n, m;
int a[N], dis[N], l[N], r[N];

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);

    cin >> n >> m;
    for(int i = 1; i <= n; i ++)
        cin >> a[i];
    
    for(int i = 1, u, v; i <= m; i ++) {
        cin >> u >> v;
        g[u].push_back(v);
        g[v].push_back(u);
    }
    fill(dis + 2, dis + n + 1, 1000000000);
    priority_queue<pii, vector<pii>, greater<pii> > q;
    q.push({0, 1});
    while(q.size()) {
        auto [d, u] = q.top();
        q.pop();
        if(d > dis[u]) continue;
        for(int v : g[u]) {
            if(d + 1 + max(a[v] - r[u] - 1, 0) < dis[v]) {
                dis[v] = d + 1 + max(a[v] - r[u] - 1, 0);
                q.push({dis[v], v});
                l[v] = 1e9;
                r[v] = -1e9;
            }
            if(d + 1 + max(a[v] - r[u] - 1, 0) == dis[v]) {
                l[v] = min(l[v], max(l[u] - 1, a[v]));
                r[v] = max(r[v], max(r[u] + 1, a[v]));
            }
        }
    }
    cout << dis[n] + l[n];
}