#include<bits/stdc++.h>
using namespace std;
int n;
int d[10010];
long long ans;
bool flag[10010];
int main(){
	cin>>n;
	for(int i=1;i<=n;i++){
		cin>>d[i];
	}
	for(int i=1;i<=n;i++){
		if(flag[i]==0){
			int j=i+1;
			ans+=d[i];
			//cout<<"d["<<i<<"]="<<d[i]<<endl;
			while(d[j]<=d[i] && j<=n){
				flag[j]=1;
				j++;
				//cout<<j<<endl;
			}
		}
	}
	cout<<ans<<endl;
	return 0;
}