// #include <me>
#include <bits/stdc++.h>
using namespace std;
#define endl "\n"
#define pb push_back
#define int long long
const int N = 3e5 + 5, M = 1e9 + 7, LG = 20;
int n , u , v , A[N] , m;
void solve(){
cin >> n >> m;
int ans = 0 , cr = 0 , mx = 0;
for (int i = 1 ; i <= n ; i++){
cin >> A[i];
}
for (int i = 2 ; i <= n ; i++){
if (A[i] <= cr){
ans++;
continue;
}else{
ans += (A[i] - cr);
cr = A[i];
}
}
for (int i = n-1 ; i >= 1 ; i--){
if (A[i] > mx){
cr--;
mx = A[i];
}
}
ans += (max((int)0 , cr));
for (int i = 1 ; i <= m ; i++){
cin >> u >> v;
}
cout << ans << endl;
}
signed main(){
ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int ts = 1;
// cin >> ts;
while(ts--){
solve();
}
}
