#include <bits/stdc++.h>
using namespace std;
typedef pair<int, int> pii;
#define ff first
#define ss second
#define MP make_pair
const int mxn = 1e6 + 10;
int dis[mxn], a[mxn], n, m;
vector<int> adj[mxn];
int main() {
cin >> n >> m;
for(int i = 1; i <= n; i++)
cin >> a[i];
for(int i = 0; i < m; i++) {
int u, v;
cin >> u >> v;
adj[u].push_back(v);
adj[v].push_back(u);
}
memset(dis, -1, sizeof dis);
priority_queue<pii> pq;
pq.push(MP(0, 1));
while(pq.size()) {
int d = -pq.top().ff;
int u = pq.top().ss;
pq.pop();
if(dis[u] > -1) continue;
dis[u] = d;
for(int v : adj[u])
if(dis[v] == -1)
pq.push(MP(-(d + max(1, abs(a[v] - a[u]))), v));
}
cout << dis[n] << endl;
return 0;
}
/*
6 7
0 100 10 7 8 0
1 3
1 2
2 3
3 4
3 5
2 5
2 6
*/
