#include<fstream.h>
unsigned long st,dr,m,p,x,s;
void zero(int a){
     unsigned long pw=5;
     long c;
     s=0;
     while(pw<a){
	  c=a/pw;
	  s+=c;
	  pw*=5;}
	  }
void jumate(){
     if(s>p){
	 dr=m;
	 m=(dr+st)/2;}
     else if(s<p){
	 st=m;
	 m=(dr+st)/2;}
     if(dr-st==1)m=dr;}
int main()
{ifstream fin("fact.in");
ofstream fout("fact.out");
st=1; dr=10000000;
m=(dr+st)/2;
fin>>p;
while(s!=p){
     zero(m);
     jumate();
     }
if(m%5!=0)m-=m%5;
fout<<m;
fout.close();
fin.close();
return 0;
}