fn main() {
    let stdin = std::io::read_to_string(std::io::stdin()).unwrap();
    let mut stdin = stdin.split_ascii_whitespace();

    let n: usize = stdin.next().unwrap().parse().unwrap();
    let logs: Vec<Vec<String>> = (0..n)
        .map(|_| {
            (0..n)
                .map(|_| stdin.next().unwrap().parse().unwrap())
                .collect()
        })
        .collect();

    println!("{}", output(solve(n, logs)));
}

fn solve(n: usize, logs: Vec<Vec<String>>) -> Option<u8> {
    let candidates = (0..n as u8)
        .filter(|&j| {
            logs.iter()
                .all(|l| l[j as usize] == "nyanpass" || l[j as usize] == "-")
        })
        .collect::<Vec<_>>();
    if candidates.len() == 1 {
        Some(*candidates.last().unwrap() + 1)
    } else {
        None
    }
}

fn output(ans: Option<u8>) -> String {
    match ans {
        Some(ans) => ans.to_string(),
        None => String::from("-1"),
    }
}