diff --git a/10.radixSort.md b/10.radixSort.md
index 2da94b8..051b6ac 100644
--- a/10.radixSort.md
+++ b/10.radixSort.md
@@ -27,6 +27,8 @@ var counter = [];
 function radixSort(arr, maxDigit) {
     var mod = 10;
     var dev = 1;
+    var max = Math.max(...arr);
+    maxDigit = typeof maxDigit !== 'number' ? maxDigit : (max + '').length;
     for (var i = 0; i < maxDigit; i++, dev *= 10, mod *= 10) {
         for(var j = 0; j < arr.length; j++) {
             var bucket = parseInt((arr[j] % mod) / dev);