fn run() {
    input! {
        n: usize,
        m: usize,
        v: [i64; n],
        s: [bytes; n],
    }
    let s = s
        .iter()
        .map(|s| s.iter().fold(0, |s, a| 2 * s + (*a == b'o') as usize))
        .collect::<Vec<_>>();
    let mut sum = vec![0; 1 << m];
    for (s, v) in s.into_iter().zip(v) {
        sum[s] += v;
    }
    bitwise_transform(&mut sum, |a, b| *b += *a);
    let mask = (1 << m) - 1;
    let sum = sum;
    let mut dp = vec![0; 1 << m];
    for i in 0..(1 << m) {
        let v = dp[i];
        for j in 0..m {
            if i >> j & 1 == 0 {
                dp[i | (1 << j)].chmax(v + (sum[mask ^ i] - sum[mask ^ i ^ (1 << j)]).pow(2));
            }
        }
    }
    println!("{}", dp[(1 << m) - 1]);
}

fn main() {
    run();
}

// ---------- begin chmin, chmax ----------
pub trait ChangeMinMax {
    fn chmin(&mut self, x: Self) -> bool;
    fn chmax(&mut self, x: Self) -> bool;
}

impl<T: PartialOrd> ChangeMinMax for T {
    fn chmin(&mut self, x: Self) -> bool {
        *self > x && {
            *self = x;
            true
        }
    }
    fn chmax(&mut self, x: Self) -> bool {
        *self < x && {
            *self = x;
            true
        }
    }
}
// ---------- end chmin, chmax ----------
// ---------- begin bitwise transform ----------
pub fn bitwise_transform<T, F>(a: &mut [T], mut f: F)
where
    F: FnMut(&mut T, &mut T),
{
    let n = a.len().trailing_zeros() as usize;
    assert!(a.len() == 1 << n);
    for i in 0..n {
        for a in a.chunks_exact_mut(2 << i) {
            let (x, y) = a.split_at_mut(1 << i);
            for (x, y) in x.iter_mut().zip(y) {
                f(x, y);
            }
        }
    }
}
// ---------- end bitwise transform ----------
// ---------- begin input macro ----------
// reference: https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8
#[macro_export]
macro_rules! input {
    (source = $s:expr, $($r:tt)*) => {
        let mut iter = $s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
    ($($r:tt)*) => {
        let s = {
            use std::io::Read;
            let mut s = String::new();
            std::io::stdin().read_to_string(&mut s).unwrap();
            s
        };
        let mut iter = s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
}

#[macro_export]
macro_rules! input_inner {
    ($iter:expr) => {};
    ($iter:expr, ) => {};
    ($iter:expr, $var:ident : $t:tt $($r:tt)*) => {
        let $var = read_value!($iter, $t);
        input_inner!{$iter $($r)*}
    };
}

#[macro_export]
macro_rules! read_value {
    ($iter:expr, ( $($t:tt),* )) => {
        ( $(read_value!($iter, $t)),* )
    };
    ($iter:expr, [ $t:tt ; $len:expr ]) => {
        (0..$len).map(|_| read_value!($iter, $t)).collect::<Vec<_>>()
    };
    ($iter:expr, chars) => {
        read_value!($iter, String).chars().collect::<Vec<char>>()
    };
    ($iter:expr, bytes) => {
        read_value!($iter, String).bytes().collect::<Vec<u8>>()
    };
    ($iter:expr, usize1) => {
        read_value!($iter, usize) - 1
    };
    ($iter:expr, $t:ty) => {
        $iter.next().unwrap().parse::<$t>().expect("Parse error")
    };
}
// ---------- end input macro ----------