kth smallest number in a multiplication table

/*
Nearly every one have used the Multiplication Table. But could you find out the k-th smallest number quickly from the multiplication table?

Given the height m and the length n of a m * n Multiplication Table, and a positive integer k, you need to return the k-th smallest number
in this table.

Example 1:
Input: m = 3, n = 3, k = 5
Output: 
Explanation: 
The Multiplication Table:
1	2	3
2	4	6
3	6	9

The 5-th smallest number is 3 (1, 2, 2, 3, 3).
Example 2:
Input: m = 2, n = 3, k = 6
Output: 
Explanation: 
The Multiplication Table:
1	2	3
2	4	6

The 6-th smallest number is 6 (1, 2, 2, 3, 4, 6).
Note:
The m and n will be in the range [1, 30000].
The k will be in the range [1, m * n]
*/

class Solution {
public:
    int findKthNumber(int m, int n, int k) {
        int low=1, high=m*n;
        while(low<=high){
            int mid= low + (high-low)/2;
            int count = enough(mid,m,n,k);
            if(count < k){
                low = mid+1;
            }
            else high=mid-1;
        }
return low;
    }
    
     int enough(int x, int m, int n, int k) {
        int count = 0;
        for (int i = 1; i <= m; i++) {
            count += min(x / i, n);
        }
        return count;
    }
};