#[macro_use]
#[allow(dead_code, unused_macros, non_upper_case_globals)]
mod io {
    macro_rules! p {
        ($x:expr) => {
            println!("{}", $x);
        };
        ($x:expr, $($y:expr),+) => {
            print!("{} ", $x);
            p!($($y),+);
        };
    }

    macro_rules! dump {
        ($($a:expr),+) => {{
            if USE_DUMP {
                use std::io::*;
                write!(stderr(), "{}:{}\t", file!(), line!()).unwrap();
                dump!(A $($a),+);
                write!(stderr(), " = ").unwrap();
                dump!(B $($a),+);
                writeln!(stderr(), "").unwrap();
            }
        }};
        (A $x:expr) => {
            write!(stderr(), "{}", stringify!($x)).unwrap();
        };
        (A $x:expr, $($y:expr),+) => {
            write!(stderr(), "{}, ", stringify!($x)).unwrap();
            dump!(A $($y),+);
        };
        (B $x:expr) => {
            write!(stderr(), "{:?}", $x).unwrap();
        };
        (B $x:expr, $($y:expr),+) => {
            write!(stderr(), "{:?}, ", $x).unwrap();
            dump!(B $($y),+);
        };
    }

    pub trait Scan<T> {
        fn scan() -> T;
    }

    macro_rules! scan_primitive {
        ($t: ty) => {
            impl Scan<$t> for $t {
                fn scan() -> $t {
                    get_word().expect("EOF?").parse()
                        .unwrap_or_else(|e| panic!("Cannot parse {}", e))
                }
            }
        };
        ($t: ty, $($u: ty),+) => {
            scan_primitive!($t);
            scan_primitive!($($u),+);
        };
    }

    macro_rules! scan_tuple {
        ($($t: ident),*) => {
            impl< $($t: Scan<$t>),* > Scan< ( $($t),* ) > for ( $($t),* ) {
                fn scan() -> ( $($t),* ) {
                    ( $( $t::scan()),* )
                }
            }
        };
    }

    scan_primitive!(u8,
                    u16,
                    u32,
                    u64,
                    i8,
                    i16,
                    i32,
                    i64,
                    f32,
                    f64,
                    usize,
                    isize,
                    bool,
                    String);
    scan_tuple!(A, B);
    scan_tuple!(A, B, C);
    scan_tuple!(A, B, C, D);

    pub fn get<T: Scan<T>>() -> T {
        T::scan()
    }

    pub fn get_vec<T: Scan<T>>(n: usize) -> Vec<T> {
        (0..n).map(|_| get()).collect()
    }

    pub fn get_mat<T: Scan<T>>(r: usize, c: usize) -> Vec<Vec<T>> {
        (0..r).map(|_| get_vec(c)).collect()
    }

    pub fn get_vec_char() -> Vec<char> {
        get_word().unwrap().chars().collect()
    }

    pub fn get_mat_char(h: usize) -> Vec<Vec<char>> {
        (0..h).map(|_| get_vec_char()).collect()
    }

    pub fn get_line() -> String {
        get_line_wrapped().unwrap()
    }

    fn get_word() -> Option<String> {
        let mut res = String::with_capacity(16);
        while let Some(c) = get_u8() {
            let d = c as char;
            if !d.is_whitespace() {
                res.push(d);
            } else if res.len() != 0 {
                unget_u8(c);
                break;
            }
        }
        if res.len() == 0 { None } else { Some(res) }
    }

    pub fn get_line_wrapped() -> Option<String> {
        let c = get_u8();
        if c.is_none() {
            return None;
        }
        let mut line = String::with_capacity(20);
        line.push(c.unwrap() as char);
        loop {
            let c = get_u8();
            if c.is_none() || c.unwrap() == b'\n' {
                // コメントはC++等での仕様
                // if c.is_some() {
                //     self.unget_u8(b'\n');
                // }
                return Some(line);
            }
            line.push(c.unwrap() as char);
        }
    }

    static mut idx: usize = 0;
    static mut len: usize = 0;
    static mut buf: [u8; 65536] = [0; 65536];

    fn get_u8() -> Option<u8> {
        unsafe {
            use std::io::{stdin, Read};
            if idx == len {
                match stdin().read(&mut buf) {
                    Ok(l) if l > 0 => {
                        idx = 0;
                        len = l;
                    }
                    _ => return None,
                }
            }
            idx += 1;
            Some(buf[idx - 1])
        }
    }

    fn unget_u8(c: u8) {
        unsafe {
            idx -= 1;
            buf[idx] = c;
        }
    }

    pub fn has_next() -> bool {
        loop {
            let c = get_u8();
            if c.is_none() {
                return false;
            }
            let c = c.unwrap();
            if !(c as char).is_whitespace() {
                unget_u8(c);
                return true;
            }
        }
    }

    pub const USE_DUMP: bool = true;
}

use io::*;

fn main() {
    while has_next() {
        let f = || {
            let mut size = 0;
            let mut next = [26; 26];
            let mut cs = vec![];
            let n = get();
            for _ in 0..n {
                let s = get_vec_char().iter()
                    .map(|c| *c as usize - b'A' as usize).collect::<Vec<_>>();
                for i in 1..s.len() {
                    next[s[i-1]] = s[i]
                }
                for &c in s.iter() {
                    cs.push(c);
                }
                size += s.len();
            }
            (size, next, cs)
        };
        let mut ok = true;
        let (sz1, next1, cs1) = f();
        let (sz2, next2, cs2) = f();
        let mut cs = cs1.iter().chain(cs2.iter()).collect::<Vec<_>>();
        cs.sort();
        cs.dedup();
        ok &= sz1 == sz2;
        let next = (0..26).map(|i| {
            if next1[i] == 26 {
                next2[i]
            } else if next2[i] == 26 {
                next1[i]
            } else if next1[i] == next2[i] {
                next1[i]
            } else {
                ok = false;
                100
            }
        }).collect::<Vec<_>>();
        let mut out = false;
        if ok {
            for &x in cs.iter() {
                let mut res = vec![];
                let mut c = *x;
                while c != 26 {
                    res.push(c);
                    c = next[c];
                }
                if res.len() == sz1 {
                    p!(res.iter().map(|c| (*c + b'A' as usize) as u8 as char)
                       .collect::<String>());
                    out = true;
                }
            }
            //dump!(res);
        }
        if !ok || !out {
            p!(-1);
        }
    }
}