use std::io::Read;
use std::collections::HashSet;

fn main() {
    let mut all_data = String::new();
    std::io::stdin().read_to_string(&mut all_data).ok();
    let all_data: Vec<&str> = all_data.trim().split('\n').map(|s| s.trim()).collect();
    if all_data.iter().skip(1).next().unwrap().split_whitespace().collect::<Vec<_>>().len() > 1 {
        println!("\"assert\"");
    } else {
        let values: Vec<usize> = all_data.iter().skip(1).take(3).map(|s| s.parse::<usize>().unwrap()).collect();
        let summary: usize = values.iter().sum();
        let mut result: Vec<usize> = values.iter().map(|i| summary - i).collect::<HashSet<usize>>().iter().map(|i| *i).collect();
        result.sort_by_key(|a| -1 * (*a as isize));
        println!("{}", result[1]);
    }
}