#include <bits/stdc++.h>
using namespace std;
#define sz(x) (int)x.size()
#define all(x) x.begin() , x.end()
const int inf = 1e9 + 7;
void solve(){
int n,m;
cin >> n >> m;
int a[n];
for(int i = 0;i<n;i++)
cin >> a[i];
vector<int>graph[n];
for(int i = 0;i<m;i++){
int u,v;
cin >> u >> v;
u-- , v--;
graph[u].push_back(v);
graph[v].push_back(u);
}
int dist1[n] , height1[n] , vis1[n] = {0};
priority_queue<array<int,3>>bfs;// -dist , node , height
bfs.push({0,0,0});
while(!bfs.empty()){
auto tmp = bfs.top();
bfs.pop();
if(vis1[tmp[1]])continue;
vis1[tmp[1]] = 1;
dist1[tmp[1]] = -tmp[0];
height1[tmp[1]] = tmp[2];
for(auto itr : graph[tmp[1]]){
bfs.push({tmp[0] - (max(tmp[2]+1,a[itr]) - tmp[2]) , itr , max(tmp[2]+1,a[itr])});
}
}
int dist2[n] , height2[n] , vis2[n] = {0};
while(!bfs.empty())bfs.pop();
bfs.push({0,n-1,0});
while(!bfs.empty()){
auto tmp = bfs.top();
bfs.pop();
if(vis2[tmp[1]])continue;
vis2[tmp[1]] = 1;
dist2[tmp[1]] = -tmp[0];
height2[tmp[1]] = tmp[2];
for(auto itr : graph[tmp[1]]){
bfs.push({tmp[0] - (max(tmp[2]+1,a[itr]) - tmp[2]) , itr , max(tmp[2]+1,a[itr])});
}
}
int ans = inf;
for(int i = 0;i<n;i++){
// node max
// cout << i+1 << " : " << dist1[i] + dist2[i] + abs(height1[i] - height2[i]) << endl;
ans = min(ans , dist1[i] + dist2[i] + abs(height1[i] - height2[i]));
// edge max
for(auto itr : graph[i]){
// cout << i+1 << " " << itr+1 << " : " << dist1[i] + dist2[itr] + abs(height1[i] - height2[itr]) << endl;
ans = min(ans , dist1[i] + dist2[itr] + abs(height1[i] - height2[itr]) + 1);
}
}
cout << ans << endl;
}
signed main(){
ios_base::sync_with_stdio(0);cin.tie(0);
int testcase=1;//cin >> testcase;
while(testcase--)solve();
cerr << 1000.0 * clock() / CLOCKS_PER_SEC << " ms" << endl;
}
