function main(input) {
  let [b] = getIntegers(input);
  let [n] = getIntegers(input);
  let c = input.map(x => Number(x)).sort((a, b) => b - a);
  
  let ans = 0;
  if(n > 1) {
    if(n % 2 == 1) {
      const index = Math.round(n / 2) - 1;
      ans = solve(c[index], b, c);
    } else {
      const index1 = Math.round(n / 2) - 1;
      const index2 = Math.round(n / 2);
      ans = Math.min(solve(c[index1], b, c), solve(c[index2], b, c));
    }
  }
  console.log(ans);
}

function solve(v, b, c) {
  let num = 0;
  for(let i=0; i<c.length; i++) {
    if(c[i] > v) {
      b += (c[i] - v);
      num += (c[i] - v);
    } else if(c[i] < v) {
      b -= (v - c[i]);
      num += (v - c[i]);
    }
  }
  return num;
}

//-- functions ------------------------------------

function getIntegers(lines) {
  return lines.shift().split(" ").map(function(e) {
    return Number(e);
  });
}

function getStrings(lines) {
  return lines.shift().split(" ");
}

function twoDimensionalArray(h, w, value) {
  const list = new Array(h);
  for(let i=0; i<h; i++) {
    list[i] = new Array(w).fill().map(function(e) {
      return value.constructor == Array ? Array.from(value) : value;
    });
  }
  return list;
}

//-- Array -------------------------------------------

Array.prototype.pushNoSameValue = function(...values) {
  values.forEach(function(e) {
    if(!this.includes(e)) {
      this.push(e);
    }
  }, this);
};

Array.prototype.sortByIntegers = function() {
  this.sort(function(a, b) {
    return a - b;
  });
};

Array.prototype.oneLineString = function() {
  let str = "";
  this.forEach(function(e, i) {
    if(i > 0) str += " ";
    str += e;
  });
  return str;
};

main(require("fs").readFileSync("/dev/stdin", "utf8").split("\n"));