Problem:
Score : 300 points

Problem Statement

Tak has N cards. On the i-th (1 \leq i \leq N) card is written an integer x_i.
He is selecting one or more cards from these N cards, so that the average of the integers written on the selected cards is exactly A.
In how many ways can he make his selection?

Constraints

1 \leq N \leq 50

1 \leq A \leq 50

1 \leq x_i \leq 50

N,\,A,\,x_i are integers.

Partial Score

200 points will be awarded for passing the test set satisfying 1 \leq N \leq 16.

Input

The input is given from Standard Input in the following format:

N A
x_1 x_2 ... x_N

Output

Print the number of ways to select cards such that the average of the written integers is exactly A.

Sample Input 1

4 8
7 9 8 9

Sample Output 1

5

The following are the 5 ways to select cards such that the average is 8:

Select the 3-rd card.

Select the 1-st and 2-nd cards.

Select the 1-st and 4-th cards.

Select the 1-st, 2-nd and 3-rd cards.

Select the 1-st, 3-rd and 4-th cards.

Sample Input 2

3 8
6 6 9

Sample Output 2

0

Sample Input 3

8 5
3 6 2 8 7 6 5 9

Sample Output 3

19

Sample Input 4

33 3
3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3

Sample Output 4

8589934591

The answer may not fit into a 32-bit integer.

Solution in JavaScript (node.js v5.12) (judge verdict: Wrong Answer)

var obj = init();
Main();
function nextInt(){return myconv(next(),1);}
function nextStrArray(){return myconv(next(),2);}//半角スペース分割
function nextIntArray(){return myconv(next(),4);}//半角スペース + 数値化
function nextCharArray(){return myconv(next(),6);}//1文字分割
function next(){return obj.next();}
function hasNext(){return obj.hasNext();}
function myin(){return require("fs").readFileSync("/dev/stdin", "utf8").trim().split("\n");}
function init(){
  var inputFile = myin();
  var returnObj = {
    "list" : inputFile, "index" : 0, "max" : inputFile.length,
    "hasNext" : function(){return (this.index < this.max);},
    "next" : function(){if(!this.hasNext()){throw "ArrayIndexOutOfBoundsException これ以上ないよ";}else{var returnInput = this.list[this.index];this.index++;return returnInput;}}
  };
  return returnObj;
}
function myout(t){console.log(t);}//標準出力
function myerr(t){console.error(t);}//標準エラー出力
//[no]要素の扱い。数値型
//不明値、異常時:引数そのまま返す　1:数値へ変換
//2:半角SPで分割 4:半角SPで分割し、数値配列へ
//6:1文字で分割  7:1文字で分割し、数値配列へ
//8:半角SPで結合 9:改行で結合 0:文字なしで結合
function myconv(i,no){try{switch(no){case 1:return parseInt(i);case 2:return i.split(" ");case 4:return i.split(" ").map((a)=>Number(a));case 6:return i.split("");case 7:return i.split("").map((a)=>Number(a));case 8:return i.join(" ");case 9:return i.join("\n");case 0:return i.join("");default:return i;}}catch(e){return i;}}
function Main(){
  var one = nextIntArray();
  var N = one[0];
  var A = one[1];
  var list = nextIntArray();
  var dp = new Array(2501).fill(0);
  for(var i = 1; i <= N; i++){
    var val = list[i - 1];
    for(var j = 2500; j >= val; j--){
      if(dp[j - val] > 0){
        dp[j] = dp[j] + dp[j - val];
      }
    }
    dp[val]++;
  }
  var output = 0;
  var count = 1;
  while(2500 >= count * A){
    output += dp[count * A];
    count++;
  }
  myout(output);
}