#include<fstream.h>


int min(int a,int b)
{
if(a>b) return b;
return a;
}

int main()
{

ifstream f("fact.in");
ofstream h("fact.out");
unsigned long p,n=1,q=0,m=0,x,t=0;

f>>p;
if(p==0) h<<1;
else
 {
 while(q!=p)

   {
   if(n%2==0) {x=n; while(x%2==0) {t++;x/=2;}}
   if(n%5==0) {x=n; while(x%5==0) {m++;x/=5;}}
   q+=min(t-q,m-q);
   n++;
   }

 h<<n-1;
 }



return 0;
}