fn main() {
    let n = {
        let mut line = String::new();
        std::io::stdin().read_line(&mut line).unwrap();
        line.trim().parse::<usize>().unwrap()
    };
    let mut ss: Vec<Vec<char>> = vec![];
    for _ in 0..n {
        let mut line = String::new();
        std::io::stdin().read_line(&mut line).unwrap();
        ss.push(line.trim().chars().collect());
    }

    let ans: String = (0..n)
        .map(|i| if ss[i][i] == 'a' { 'b' } else { 'a' })
        .collect();
    println!("{}", ans);
}