#include <iostream>
#include <fstream>

std::ifstream input("fact.in");
std::ofstream output("fact.out");

int count2(int N)
{
	int contor = 0;
	while( N % 2 == 0 )
	{
		++contor;
		N = N / 2;
	}
	return contor;
}

int count5(int N)
{
	int contor = 0;
	while( N % 5 == 0 )
	{
		++contor;
		N = N / 5;
	}
	return contor;
}

int main(int argc, char* argv[] )
{
	int P;
	input >> P;
	int contor = 0;
	int N = 1;
	int nr2 = 0;
	int nr5 = 0;
	while ( contor < P )
	{
		++N;
		nr2 += count2(N);
		nr5 += count5(N);
		contor = std::min( nr2, nr5 ); 
	}
	output << N;
	return 0;
}