#include <bits/stdc++.h>
#define f first
#define s second
#define pb push_back
#define mp make_pair
#define ll long long
using namespace std;
const ll N=1e6;
ll mod=1e9+7;
ll a[N+5],l,r,x,y,z,ans,t,n,q,mx,mn,k,m;
bool ok,okk;
string s,s1;
vector <ll> v[N+5];
int main(){
ios_base::sync_with_stdio(false);
cin.tie(0),cout.tie(0);
cin >> n >> m;
for (int i=1; i<=n; i++) cin >> a[i];
for (int i=1; i<=m; i++){
cin >> x >> y;
v[x].pb(y);
v[y].pb(x);
}
ll cur=0,ans=0;
for (int i=2; i<n; i++){
if (cur<a[i]){
ans+=a[i]-cur; cur=a[i];
}
else
if (cur==a[i]) ans++;
else
{
ans++; cur--;
}
}
ans+=cur;
cout<<ans<<endl;
}
