use std::io::Read;

const INF:usize=usize::MAX>>2;

fn main(){
    let mut input = "".to_owned();
    std::io::stdin().read_to_string(&mut input).unwrap();
    let mut input = input.split_ascii_whitespace();
    macro_rules! read(($ty:ty) => (input.next().unwrap().parse::<$ty>().unwrap()));

    let n=read!(usize);
    let mut v=vec![!0;n];

    for i in 0..n{
        v[i]=read!(usize);
    }
    
    if n==1{
        println!("{}",v[0]);
    }
    else if n==2{
        println!("{}",v[0].max(v[1]));
    }
    else{
        let mut dp=vec![INF;n];
        dp[0]=v[0];
        dp[1]=v[1];
    
        for i in 2..n{
            dp[i]=dp[i-1];
            for j in 0..i-1{
                dp[i]=dp[i].max(dp[j]+v[i]);
            }
        }
    
        println!("{}",dp[n-1]);
    }
}