///TRAN THAI BAO :3
#include <iostream>
#include <cstdio>
#include <vector>
#include <queue>
using namespace std;
#define maxN 200007
#define oo 1e18
typedef pair<long long, long long> pii;
typedef pair<pii, long long> piii; //dist - node - layer
int n, m;
long long a[maxN];
long long minD[maxN][2];
vector<int>adj[maxN];
priority_queue<piii, vector<piii>, greater<piii> >pq;
void readData()
{
cin >> n >> m;
for(int i = 1; i <= n; i++)
{
cin >> a[i];
minD[i][0] = minD[i][1] = oo;
}
minD[1][0] = 0;
int u, v;
for(int i = 0; i < m; i++)
{
cin >> u >> v;
adj[u].push_back(v);
adj[v].push_back(u);
}
}
void solve()
{
pq.push({{minD[1][0], 1}, 0});
while(!pq.empty())
{
piii cur = pq.top();
pq.pop();
if(minD[cur.first.second][cur.second] != cur.first.first)
continue;
int u, v, layer;
long long w;
u = cur.first.second;
layer = cur.second;
for(int i = 0; i < adj[u].size(); i++)
{
v = adj[u][i];
if(layer == 0)
{
if(a[v] < a[u])
continue;
w = max(a[v] - a[u], 1ll);
}
else
{
if(a[v] > a[u])
continue;
w = max(a[u] - a[v], 1ll);
}
if(minD[v][layer] > minD[u][layer] + w)
{
minD[v][layer] = minD[u][layer]+w;
pq.push({{minD[v][layer], v}, layer});
}
}
if(layer == 0)
if(minD[u][1] > minD[u][0])
{
minD[u][1] = minD[u][0];
pq.push({{minD[u][1], u}, 1});
}
}
cout << minD[n][1];
}
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
readData();
solve();
return 0;
}
