#include <stdio.h>
int main()
{long long int  x,st,dr,k,i,s,v[100000],nr;
 freopen("factorial.in","r",stdin);
 freopen("factorial.out","w",stdout);
 scanf("%lld",&k);
 if (k<=4) x=k*5; else
 {
 st=0;dr=k*5;nr=1;v[nr]=5;
  for( ; ;)
  {
   if (dr==st+1) {x=-1; break;}
    s=0;x=(st+dr)/2; for (;v[nr]*5<=x;) {nr+=1; v[nr]=v[nr-1]*5;}
    for (i=1;i<=nr;i++)
       s+=x/v[i];
    if (s==k) { break;} else
    if (k<s) dr=x; else
    if (k>s) st=x;

   }
  }
 if (x==-1) printf("-1"); else
 printf("%lld",(x/5)*5);
 return 0;}