use proconio::input;
fn main() {
    input! {
        n:usize,
        list: [[String;n];n],
    }
    let mut count = 0;
    let mut save = 0;
    let mut first = false;
    let mut doppelganger = false;
    for i in 0..n {
        for j in 0..n {
            if list[j][i] == "nyanpass" || list[j][i] == "-" {
                count += 1;
            }
            if count == n{
                save = i + 1;
                if first{
                    doppelganger = true;
                    break;
                }
                first = true;
            }
        }
    }
    if doppelganger || save == 0{
        println!("-1")
    }else{
        println!("{}",save)
    }
}