#include <iostream>
#include <cstring> 
#include <math.h>
using namespace std;
int decimal(int system,string number)
{
	int sum = 0;
	int l = number.length();
	int k = 0;
	for (int i = l - 1; i >= 0; i--)
	{
		if (number[i] >= 'A')
		{
			number[i] -= 55;
		}
		else
		{
			number[i] -= 48;
		}
		sum += number[i] * pow(system,k);
		k += 1;
	}
	return sum;
}
int main()
{
	int x;
	string n;
	cin >> n;
	cin >> x;
	cout << decimal(x,n);
	return 0;
}