use itertools::Itertools;
use std::io::stdin;
use std::io::BufRead;

fn main() {
    let mut prev: Option<i32> = None;
    let mut increased = 0;
    for (a, b, c) in stdin()
        .lock()
        .lines()
        .map(|line| line.unwrap().parse::<i32>().unwrap())
        .tuple_windows()
    {
        let sum = a + b + c;
        match prev {
            Some(prev) => {
                if sum > prev {
                    increased += 1
                }
            }
            _ => (),
        }
        prev = Some(sum)
    }

    println!("{}", increased)
}