#include <bits/stdc++.h>
using namespace std;
int main(){
int n, m;
cin >> n >> m;
vector<int> v(n);
vector<vector<int >> g(n);
for(auto &e:v) cin >> e;
for(int i=0; i<m; i++){
int a, b;
cin >> a >> b;
a--; b--;
g[a].push_back(b);
g[b].push_back(a);
}
vector<int> ans(n, -1), ans2(n, -1), tm(n, -1), tm2(n, -1);
priority_queue<tuple<int, int, int >> pq;
pq.push({0, 0, 0});
while(pq.size()){
auto [t, h, cur]=pq.top();
pq.pop();
if(tm[cur]!=-1) continue;
t=tm[cur]=-t;
h=ans[cur]=-h;
for(auto ch:g[cur]) pq.push({-max(v[ch], t + 1), -max(h, v[ch]), ch});
}
pq.push({0, 0, n-1});
while(pq.size()){
auto [t, h, cur]=pq.top();
pq.pop();
if(tm2[cur]!=-1) continue;
h=ans2[cur]=-h;
t=tm2[cur]=-t;
for(auto ch:g[cur]) pq.push({-max(v[ch], t + 1), -max(h, v[ch]), ch});
}
int ans_ = INT_MAX;
for(int i = 0; i < n; i++) ans_ = min(ans_, tm[i] + tm2[i] + abs(ans[i] - ans2[i]));
cout << ans_ << '\n';
}
