#include<fstream.h>
int i=0,j,k=5,p,s=0,l=0,o,u=0,aux;
int main(){
	ifstream fin("fact.in");
	fin>>p;
	fin.close();
	ofstream fout("fact.out");
	/*while(l<p)
	{   l=0;
	    k=5;
		i++;
		while(i/k)
		{
			l=l+i/k;
			k=k*5;
		}
		
	}
	fout<<i<<" ";
	*/
	j=0;
	while(u!=p)
		
	{   j++;
		aux=j;
		while(aux%5==0)
		{
			u++;
			aux=aux/5;
		}
	}
	
			
	
	fout<<j;
	

	
	
	fout.close();
	return 0;
}