#include <stdio.h>
int main()
{long long int  x,st,dr,k,i,s,v[1000],nr;
 freopen("factorial.in","r",stdin);
 freopen("factorial.out","w",stdout);
 scanf("%lld",&k);
 if (k<=4) printf("%lld",k*5); else
 {
 st=0;dr=k*5;nr=1;v[nr]=5;
  for( ; ;)
  {
   if (dr==st+1) {printf("-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) {printf("%lld",x/5*5); break;} else
    if (k<s) dr=x; else
    if (k>s) st=x;

   }
  }
 return 0;}