#include<iostream>
#include<fstream>
//#include<conio.h>
using namespace std;
int nrOfZeros(int y)
{
	int x=y;
	int nrZ=x;
	while(x>=5)
	{
		x/=5;
		nrZ+=x;
	}
	return nrZ;
}
//long maxim = 80000003;

long findTheOne(long current,long p)
{	
	long x=nrOfZeros(current);
	
	if(nrOfZeros(current) > p)
		return -1;
	if(nrOfZeros(current) == p)
		return current;
	return findTheOne(current+1,p);
}

int main()
{
	long p,n=1;

	
	ifstream f("fact.in");
	f>>p;
	f.close();

	
	n = (p==0)?1:findTheOne((p*3)/4,p);

	
	//for(long i=0;i<=100000;i+=1000)
	//	cout<<"P= "<<i<<"   N= "<<findTheOne((i*3)/4,i)<<endl;
	
	//getch();
	
	
	ofstream g("fact.out");
	g<<n<<"\n";
	g.close();
	
	
	return 0;
}