LeetCode 400. Nth Digit

public class Solution {
public int findNthDigit(int n) {
int level = 1;
long count = level * 9 * (long)Math.pow(10, level - 1);
while (n > count) {
n -= count;
level++;
count = level * 9 * (long)Math.pow(10, level - 1);
}
int div = (n - 1) / level;
int res = (n - 1) % level;
long num = (long)Math.pow(10, level - 1) + div;
return (int)(num / (long)Math.pow(10, level - res - 1) % 10);
}
}