#include<fstream.h>
ifstream f("fact.in");
ofstream g("fact.out");
int n,nf,p,nr,nr2,nr5,cn;
int main()
{ f>>p;
  n=1;
  while(nr<p) { n++;
				if(n%2==0) { cn=n;
					         while(cn%2==0) { cn/=2;
                                              nr2++;
							                }
						   }
                if(n%5==0) { cn=n;
                             while(cn%5==0) { cn/=5;
                                             nr5++;
							               }
						   }
                if(nr5>nr2) { nr+=nr2;
				              nr2=0;
				              nr5-=nr2;
				            }
				else { nr+=nr5;
				       nr5=0;
                       nr2-=nr5;
				     }					   
			  }
  g<<n;
  f.close();
  g.close();
  return 0;
}