function diagonal(n, p) {
  var diag = [], one=[], elem = [];
  elem[0]=1;
  for (var i=n; i>=0; i--) {
    for (var j=0; j<=i; j++) {
      if (i===n) {
        one.push(1);
        diag[i]=one;
      }
      if (i===n-1) {
         elem[j+1]=(elem[j]+diag[i+1][j+1]);
            if (j===n-1) {
            elem.pop();
            }
        diag[i]=elem.slice();
      }
      if (i<n-1) {
         elem[j+1]=(elem[j]+diag[i+1][j+1]);
            if (j===i) {
            elem.pop();
            }
        diag[i]=elem.slice();
      }
    }
  }

  diag.reverse();
  var total = diag[p].reduce(function(a, b) {
  return a + b;
  });
  return total;
}