#include <iostream>
using namespace std;

int main()
{
	long long n, k;
	cin >> n >> k;
	if (n <= k)
		cout << n << endl;
	else
	{
		unsigned long long sum = 1;
		long long r = 1LL*1000000000*1LL*1000000000;
		bool flag = true;
		long long m1 = 0;
		for (long long i = n; i > 1; i=i-k)
		{
			sum *= i;
			if (sum > r)
			{
				flag = false;
				cout << "overflow" << endl;
				break;
			}
		}
		if (flag == true)
			cout <<sum << endl;
	}
	system("pause");
	return 0;
}