#include <fstream>
#include <iostream>
using namespace std;


long numarde0(long long i)
{
long j=0;
while(i%5==0)
{
	i=i/5;
	j++;
}
return j;
}

int main()
{
	long long n=0;
	long long sum=0;
	long long i=5;
	ifstream f("fact.in");
	ofstream g("fact.out");
	f>>n;
	
	while(sum<n)
	{

	sum=sum+numarde0(i);
		
	i=i+5;


	}
	g<<i-5;
	return 0;
}