#include<stdio.h>
using namespace std;
int desc(int a)
{


 int j,k,i;
    j=0;
   for(i=1;i<=a;i++)
   {
      k=i;
       while(k%5==0)
       {
          k=k/5;
           j++;
       }
   }
   return j;
}
int main()
{
int p;

FILE *fp;
fp=fopen("fact.in","r");
fscanf(fp,"%d",&p);





     int i,y,x;
     y=2;
     for(i=0;i<=y;i++)
     {
         y++;
         if(desc(i)==p)
         {
             x=i;
             break;
         }
     }
     if(p==0)
     {
         x=1;
     }
 FILE *fw;
 fw=fopen("fact.out","w");
 fprintf(fw,"%d",x);
 fclose(fp);
 fclose(fw);


}