백준 1300 c++

#include <iostream>
#include <vector>

using namespace std;

long long int input(long long int lower, long long int upper)
{
	//cout << "input()" << endl;
	long long int A;

	while (1)
	{
		cin >> A;
		if (A >= lower && A <= upper)
		{
			break;
		}
		else
		{
			;
		}
	}

	return A;
}

long long int find_result(int N, int k)
{
	int i;
	int left = 1;
	int mid;
	int right = k;
	int result = 0;
	int count;

	while (1)
	{
		if (left > right)
		{
			break;
		}
		else
		{
			count = 0;
			mid = (left + right) / 2;
			for (i = 1; i <= N; i++)
			{
				count = count + min(N, mid / i);
			}
			if (count >= k)
			{
				result = mid;
				right = mid - 1;
			}
			else
			{
				left = mid + 1;
			}
		}
	}

	return result;
}

int main(void)
{
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	cout.tie(NULL);

	long long int N, k;

	N = input(1, 100000);
	k = input(1, N * N);
	cout << find_result(N, k) << "\n";

	return 0;
}