<p>Given two integers <code>n</code> and <code>k</code>, return <em>the</em> <code>k<sup>th</sup></code> <em>lexicographically smallest integer in the range</em> <code>[1, n]</code>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> n = 13, k = 2
<strong>Output:</strong> 10
<strong>Explanation:</strong> The lexicographical order is [1, 10, 11, 12, 13, 2, 3, 4, 5, 6, 7, 8, 9], so the second smallest number is 10.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> n = 1, k = 1
<strong>Output:</strong> 1
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= k &lt;= n &lt;= 10<sup>9</sup></code></li>
</ul>

class Solution {
public:
    int f(long long n, long long cur, long long end){
        int steps = 0;
        while(cur <= n){
            steps += min(n+1ll,end)-cur;
            cur*=10;
            end*=10;
        }
        return steps;
    }
    int findKthNumber(int n, int k) {
        int cur = 1;
        k--;
        while(k>0){
            int steps = f(n,cur,cur+1);
            if(steps<=k){
                cur++;
                k-=steps;
            } else{
                cur*=10;
                k--;
            }
        }
        return cur;
    }
};
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