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

    let sss: Vec<Vec<usize>> = ccc
        .iter()
        .map(|cc| cc.iter().map(|&c| (c as u8 - b'0') as usize).collect())
        .collect();

    let mut min_max = vec![0; 1 << k];
    let mut min_max_indexes = vec![0; 1 << k];

    for i in 0..n {
        for bit in 1..(1 << k) {
            let min = (0..k)
                .filter(|&j| (bit >> j) & 1 == 1)
                .map(|j| sss[i][j])
                .min()
                .unwrap();

            if min >= min_max[bit] {
                min_max[bit] = min;
                min_max_indexes[bit] = i;
            }
        }
    }

    min_max_indexes.remove(0);
    min_max_indexes.sort_unstable();
    min_max_indexes.dedup();

    println!("{}", n - min_max_indexes.len());
}