function Main(input) {
    const data = input.split("\n");
    const n = data[0];
    const y = data[1].split(" ");
    y.sort();
    let sum = 0;
    if(n % 2 == 1) {
        sum = calcSum(y, Math.floor(n/2));
    } else {
        sum = (calcSum(y, n/2) + calcSum(y, n/2-1)) / 2;
    }
    console.log(sum);
}

function calcSum(y, index) {
    let sum = 0;
    const base = Number(y[index]);
    for(let i=0; i<y.length; i++) {
        sum += Math.abs(y[i] - base);
    }
    return sum;
}

Main(require("fs").readFileSync("/dev/stdin", "utf8"));