use std::io::Write;
use std::fs::File;
use std::io::BufReader;
use std::io::BufRead;


fn main() {
    let file = File::open("input.txt").expect("Cant open input file!"); 
    let reader = BufReader::new(file);

    let result: Vec<i64> = reader.lines()
        .map(|line| line.unwrap().parse::<i64>().unwrap())
        .collect();
    
    let sum: i64 = result.iter().sum();

    let mut output_buf = File::create("output.txt").expect("Cant open output file!");
    write!(&mut output_buf, "{}", sum).expect("Can not write to output file");
}