use std::io::*;
use std::str::FromStr;

#[allow(dead_code)]
fn get_line() -> String {
    let stdin = stdin();
    let mut line = String::new();
    stdin.lock().read_line(&mut line).expect("io error.");
    line.trim().to_string()
}

#[allow(dead_code)]
fn cast<T: FromStr>(s: &str) -> T {
    s.parse().ok().expect("parse error.")
}

#[allow(dead_code)]
fn get_vec<T: FromStr>() -> Vec<T> {
    (&get_line()).split(' ').map(cast::<T>).collect()
}

fn main() {
    let n: usize = cast(&get_line());
    let mut a: Vec<Vec<String>> = Vec::with_capacity(n);

    for i in 0..n {
        a.push(get_vec::<String>());
    }

    let mut ans: Vec<usize> = Vec::new();
    for j in 0..n {
        let mut renge = true;

        for i in 0..n {
            if i == j {continue;}
            if a[i][j] != "nyanpass".to_string() {
                renge = false;
            }
        }

        if renge {ans.push(j + 1)};
    }

    if ans.len() == 1 {
        println!("{}", ans[0]);
    } else {
        println!("-1");
    }
}