function solution(A) {
  var sorted = A.sort(function(a, b) {
      return a - b; 
      });
  var isPerm = 1;
  for (var i = 0, li = sorted.length; i < li; i++) {
    if (sorted[i] != (i + 1)) {
      isPerm = 0;   
      break;
    }
  }

  return isPerm;
}