use itertools::Itertools;
use proconio::{input, marker::Chars};

const HAND_KIND: [char; 3] = ['G', 'P', 'C'];

fn main() {
    input! {
        n: usize,
        m: usize,
        s: [Chars; n],
    }

    let mut ans = vec![];
    let mut is_lose = vec![false; n];
    for j in 0..m {
        let mut kinds: i32 = 0;
        for i in 0..n {
            if is_lose[i] {
                continue;
            }
            kinds |= 1 << HAND_KIND.iter().position(|c| *c == s[i][j]).unwrap()
        }
        let win_hand = match kinds.count_ones() {
            0 => 0,
            1 => {
                let mut res = 0;
                for i in 0..3 {
                    if 1 << i == kinds {
                        res = (i + 1) % 3;
                    }
                }
                res
            }
            2 => {
                if kinds == (1 << 0) | (1 << 1) {
                    1
                } else if kinds == (1 << 1) | (1 << 2) {
                    2
                } else {
                    0
                }
            }
            3 => {
                println!("-1");
                return;
            }
            _ => unreachable!(),
        };
        ans.push(HAND_KIND[win_hand]);

        for i in 0..n {
            if is_lose[i] {
                continue;
            }
            let kind = HAND_KIND.iter().position(|c| *c == s[i][j]).unwrap();
            if (kind + 1) % 3 == win_hand {
                is_lose[i] = true;
            }
        }
    }

    println!("{}", ans.iter().join(""));
}