#include<stdio.h>
#include<string.h>
int calc(int a)
{
 int gh=0;
 while(a!=0)
 {   a=a/5;
      gh=gh+a;

 }
 return gh;
}
long long x=0,q,w,m,s,d,f,z;
int N;
int main()
{freopen("fact.in","r",stdin);
freopen("fact.out","w",stdout);
     scanf("%d",&N);
     x=N*5;
     s=0;
     d=x;
     while(f==0)
     {
          z=(s+d)/2;

          m=calc(z);

          if(m==N)
          {
          f=1;
          for(int i=z;i>=z-5&&i>1;--i)
          if(calc(i)==m)
          q=i;
          }
          else if(m>N)
          {
               d=z-1;

          }
          else if(m<N)
          {
               s=z+1;
          }
          if(s>d)
          {
               f=1;
               q=-1;
          }

     }
if(N!=0)
printf("%d",q);
else
printf("%d",1);





}