use std::cmp::min;

fn calc(boxes: &Vec<usize>, base: usize) -> usize {
    boxes.iter()
        .map(|&val| if val > base { val - base } else { base - val })
        .sum()
}

fn main() {
    let mut b = String::new();
    std::io::stdin().read_line(&mut b).ok();
    let b: usize = b.trim().parse().unwrap();
    let mut n = String::new();
    std::io::stdin().read_line(&mut n).ok();
    let n: usize = n.trim().parse().unwrap();
    let mut boxes: Vec<usize> = vec![0; n];
    let mut lower: usize = 1_000_000_000;
    let mut upper: usize = b as usize;
    for i in 0..n {
        let mut c = String::new();
        std::io::stdin().read_line(&mut c).ok();
        let val: usize = c.trim().parse().unwrap();
        boxes[i] = val;
        lower = min(lower, val);
        upper += val;
    }
    upper /= n as usize;

    while upper - lower > 3 {
        let lmiddle = (2*lower + upper) / 3;
        let rmiddle = (lower + 2*upper) / 3;
        let minidx: usize = vec![lower, lmiddle, rmiddle, upper].iter()
            .map(|val| calc(&boxes, *val))
            .enumerate()
            .min_by_key(|pair| pair.1)
            .map(|pair| pair.0)
            .unwrap()
        ;
        match minidx {
            0 => { upper = lmiddle; },
            1 => { upper = rmiddle; },
            2 => { lower = lmiddle; },
            _ => { lower = rmiddle; },
        }
    }
    let lmiddle = (2*lower + upper) / 3;
    let rmiddle = (lower + 2*upper) / 3;
    let targets: Vec<usize> = vec![lower, lmiddle, rmiddle, upper];
    let minidx: usize = targets.iter()
        .map(|val| calc(&boxes, *val))
        .enumerate()
        .min_by_key(|pair| pair.1)
        .map(|pair| pair.0)
        .unwrap()
    ;
    println!("{}", calc(&boxes, targets[minidx]));
}