#include "bits/stdc++.h"
using namespace std;
#define int long long
const int N = 3e5+5;
int a[N];
vector<int> g[N];
int suf[N];
void solve(){
int n, m; cin >> n >> m;
for(int i=1; i<=n; i++) cin >> a[i];
for(int i=1; i<=n; i++) {
int x, y; cin >> x >> y;
g[x].push_back(y);
g[y].push_back(x);
}
for(int i=n; i>=1; i--) suf[i] = max(suf[i+1], a[i]);
int you = 0, ans = 0;
for(int i=2; i<=n; i++) {
if(suf[i] < you) you--;
else if(suf[i] > you) you++;
ans++;
if(you < a[i]) ans += a[i]-you, you += a[i]-you;
}
ans += you;
cout << ans << '\n';
}
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
solve();
}
