use linebuffer::{
    buf::forward,
    ParsedLines,
};
use std::{
    io,
    str,
    fs,
};

#[derive(Debug, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, Default, Copy)]
struct MaybeU64(Option<u64>);

impl str::FromStr for MaybeU64
{
    type Err = <u64 as str::FromStr>::Err;

    #[inline] 
    fn from_str(s: &str) -> Result<Self, Self::Err> {
	if s.is_empty() {
	    Ok(Self(None))
	} else {
	    Ok(Self(Some(s.parse()?)))
	}
    }
}

fn input_reader<R: io::Read>(input: R) -> ParsedLines<R, forward::FromStr<MaybeU64>>
{
    ParsedLines::new(input)
}

fn main() -> Result<(), Box<dyn std::error::Error+ 'static>> {
    let mut reader = input_reader(fs::OpenOptions::new().read(true).open("input")?);
    
    let mut last_elf = 0;
    let mut max_elf = 0;
    while let Some(res) = reader.try_next()
    {
	match res.expect("Failed to parse line").0 {
	    Some(value) => last_elf += value,
	    None if last_elf > max_elf => {
		max_elf = std::mem::replace(&mut last_elf, 0);
	    },
	    _ => last_elf = 0,
	}
    }
    println!("{}", std::cmp::max(max_elf, last_elf));
    Ok(())
}