#include<fstream>
using namespace std;
ifstream fin("factorial.in");
ofstream fout("factorial.out");
int main()
{
	int i,p,s2=0,s5=0,s,aux,gasit=0;
	
	for(i=1;!gasit;i++)
	{
		aux=i;
		while(aux%2==0)
		{
			s2++;
			aux/=2;
		}
		while(aux%5==0)
		{
			s5++;
			aux/=5;
		}
		if(s2<s5)
		{
			s+=s2;
			s5-=s2;
		}
		else
		{
			s+=s5;
			s2-=s5;
		}
		if(s==p)
		{
			fout<<i<<'\n';
			gasit=1;
		}
	}
	
		
	
	
	fin.close();
	fout.close();
	return 0;
}